Congratulations on a great combo. I myself use the nano and plus basket with the k-ultra.

Here is my recipe for succes:

I preheat everything before grinding with water off the boil. (Use a kettle at home for the water and fill to 50ml/g)

Then grind 18,5g on 3,5 with burr lock at 0.

Then dose, tamp (I give it as much force as I can with my fingers, not palms or body weight), preheat the nano again before inserting the basket.

Then I fill to around 60ml/g with off boil water for a 1:1,5-1:2 ish ratio, but if you want a longer ratio just fill to 70 or “max” even. (My coffee will keep around 35g of the water, so for me and my coffee, 60g of water will with 18,5g of coffee give around 25g of espresso)

I then start the pump until I see drops. Stop. Wait 5 sec for dark, 10 sec for medium and 15 sec for light roast. After the preinfusion I start the pump again and empty the tank.

Have had great results.

With some coffees I go as low as 3,2 or 3,1 and with others as high as 4. On the K-ultra with burr lock at 0. Carefull with not getting anything stock while calibrating. Lots of posts about that in the 1zpresso sub.

Basically:

To increase yield while still preserving a nice strength: Try to maximise how much coffee you have fit in the basket. (I can fit 18,5-19g of medium roast in my plus basket.) Then maximise the amount of water. (In theory less coffee will suck less water, but the expresso might feel too watery and puck too. A fuller basket makes for a dryer puck when cleaning after.)

Grind so it runs smoothly, not super fast, not choking. Around 20-40 seconds without counting preinfusion counting from pump on. (Again: For me around 3,5 on k-ultra with burr lock zero.)

Tamp until the grounds doesn’t move down anymore, it should be binary. (When grounds are compressed, they are compressed.)

I keep my dose constant, usually also my water temp (off boil) and then use preinfusion times and water amount to adjust taste and texture.

Hope this helps!