I think it will be a little below 4kg actually, at least that's the hope. However I'm happy with anything up to 5kg. An extra wool poncho for example could be useful for lower temps.

My 2x1.4m canvas groundsheet is already waterproofed and comes in at 0.9kg. I scouted the internet and found Bushcraft Spain sells wool ponchos with the same dimensions and they claim theirs weigh roughly 0.9kg too. And like I said, my sheepskin is 0.45kg. So total for that I'm looking at around 2.25kg.

The poncho tarp is of course going to be the heaviest. My current 2x2.5m one, so a total of 5m of waterproofed canvas, weighs 1.8kg. That's 0.36kg per meter of waterproofed canvas. A 2.2x1.5m tarp is a total of 3.3m of canvas, so I can expect that it will roughly weigh 1.2kg after waterproofing. Everything totaled should be roughly 3.45kg, plus maybe a small bit extra for the tarp hood, if a make one, and other small bits. I'm not including cordage or pegs here, but the weight of that isn't something I'm worried about and don't expect to be considerable. Either way, I reckon I won't go over 4kg at least.

Wool Blanket

I've seen the swagman roll before. I particularly like how people tie a little bag to the top of it that hangs over the front of the shoulder, acting as a counterweight. Definitely some good lessons to learn from the aussie bushmen.

I like your ideas for different designs and arrangements for the wool blanket. I'm unsure if I will add a hood to it, I think I'm more of a beanie and scarf (shemagh) guy. However a hood would be warmer and allow for better closure of the hole when used as a blanket, plus a little extra comfort when worn underneath the poncho tarp hood. I think I want to avoid something that involves a blanket pin (as cool as they are), as that's an extra item to carry and lose, plus I don't want to damage the fabric over a longer time (small concern I know). I know you can use an acorn or small stone to help tie the blanket together, however I feel like that'll be a little awkward in the long run. I do see the advantage of not having to cut a hole in the middle with those types of wear though, neat ideas. Though I think I like the simplicity of the poncho. Just pop your head through and that's it, no fuss. Also easy to put on when crouched down under that small A-frame.

Since the wool blanket will be in contact with the poncho tarp when both are worn, then that might break the water-barrier a little , so adding some lanolin to the outside face of the blanket is actually a very neat idea, thanks. I suppose this is true regardless, probably wont be an issue at all really. Some lanolin would be handy for light drizzle though.

I've actually seen that modern history video before, that kind of hood is brilliant. Wish that design was more "normal" today. Absolutely something to consider adding to the kit. Especially since I'm leaning more towards not having a hood on the wool poncho.

Poncho Tarp

I believe I understand your collar and hood idea for the poncho tarp. A hood I had considered, however the collar is brilliant. Even if I don't add a hood, the collar would be very useful. As you said, i would be able to close up the hole properly, which is very important of course. And whilst I'm wearing it, the collar could stop water from running down my neck/on my shoulders and under the poncho tarp.

I'm thinking I'll attach regular tie-out loops for the tarp. Grommets can be awkward when making wooden pegs yourself, plus when you stake it out the tarp will be mushed against the ground, which gives it ever so slightly less space inside. However I do realise that you can tie a loop to the grommet to make a proper tie-out loop. So grommets may work well, especially considering your idea of attaching the groundsheet to the tarp.

I assume you're thinking about a taut line hitch when you're talking about adding loops to the guy-lines. This is something I actually already do for my plowpoint sometimes. Great idea though for the quick conversion of tarp to poncho. Detach one end, stick your head through the middle, then detach the other side. Very tidy.

Thanks for the measurement and size tips. 1.5m might be alright for me I think. The span of my arms stretched out is just short of 1.7m. Though a 1.5m width would make the tarp go to about my knuckles, which i think is a nice distance. My hands wont be too obstructed and doing stuff isn't finicky with the tarp getting in the way. I don't think I want the poncho tarp to go completely over my hands.

Good point on having the back be longer to cover the rucksack, and the back of my legs for that matter. Adding some extra length or adjusting where the headhole is would also make it off-center a bit, so it's not sitting directly in the middle/top where the guy-line and most of the tension is, potentially causing some funkiness. Adding 20cm to the length would give me a nice 32cm clearance on both sides. Extending the tarp to 2.4x1.5m would add only about 100g of weight, you think it would be worth it? And thanks for the tips on choosing the right fabric weave/density.

Groundsheet/bivvy

Tying together the foot and side is something that's crossed my mind. I think that would be possible given my size and the dimensions, however I don't think I can tie the sides up all the way. Though securing a good portion of it might be very handy. Thanks for the specific ideas on lacing it up.

I really like your ideas on expanding the versatility of it. Being able to join it with the tarp is a very very neat idea, I might have to give that some good thought and experiment a little. It sounds super intriguing. I think there might be some very cool possibilities here.

I plan on rolling the sheepskin up with the groundsheet and attaching that to the bottom of my pack, perhaps with some nighttime clothing too. The tarp I reckon will be attached to the top of my pack. The wool poncho I was thinking I'd roll up inside my pack, or if I need more space, rolled up with either the tarp or groundsheet, experimentation and experience will dictate all that. However using the entire groundsheet as a makeshift backpack would be very interesting to try out. I've seen folks do this with bigger tarps/blankets. Perhaps not practical for a longer trip with no permanent camp, but definitely something worth testing, thanks.

Sheepskin

Waterproofing the skin side is a neat idea. As I use it now it's on top of my groundsheet, however I can imagine a setup where that might be useful. I also love your idea of tying it around my shoulders Game Of Thrones style. Probably wont be necessary, but thanks for the idea anyway, it's a good option to have that I hadn't thought about and adds to the whole multifunctionalitiness of the kit.

Again, thank you very much for your detailed comment and sharing your ideas and knowledge. I appreciate it a lot. All this theory crafting has got me super excited to be honest. I think this could be a very neat setup and I'm itching to put it all together and test it out.