I've only ever skated 2 shaped boards, one being an 8.5 Death Dave Allen "Lydia" deck that had a bit of a squarer tail and a 15" WB, the other being a Welcome Nora 8.125 on the Wicked Princess shape. Oddly, despite the disproportionate sizing between the 2 decks, I swear I had better kickflips on those two boards than I usually do - maybe squarer tails are the way forward.
I was initially skeptical as fuck of the Welcome deck but it ended up being pretty rad, my only gripe with it was that the tail was mad flat - it had some benefits, I've never really been too good at flatground and I was in the process of learning 360 shoves at the time, and the flat tail made it real easy to get a good pop/scoop for those, but I seemingly lost 360 flips whilst skating it. Probably more from hopping between random sizes and running 149s on all of em if anything.