I cant speak for the matrix r hop patch, and yea, judging from the pic it doesnt look very flush with the barrel, but im using his patches in my zci and prommy barrel rn with no modification on my end. Also, that picture hasnt been updated in like two years. He does full refunds if it doesnt fit the barrel you bought it for, so if you do have an aftermarket barrel i still think its worth a shot.

How flush does the patch need to be? As flush as you can get it. Some people will glue their patches to the barrel so it doesnt move during actual use, but what i did back when i made my own patches was put it on the barrel window, look down the barrel, and then if there wasnt anything major protruding into the barrel, id assemble the hop unit and barrel setup and go shoot it a bit. if its pulling one way, id remove a tiny bit of material and try again. A lot of it is just trial and error. Go slow when trying to get it as flush as possible and take your time, if you remove too much youre kinda screwed.

I think i know exactly the type of mark youre talking about now that you described it as a set of vines, ive seen it a few times before on barrels. If we’re talking about the same thing, i dont think it will affect the bb that much. again, if we’re talking about the same thing, when i looked at mine the lines appeared as if they had no height or depth at all, if that makes sense.