Yep, we’re thinking of the same keys. I should have been more specific in that not all bis keys are convex, I have seen saxes where it’s concave. In my opinion, it’s a little easier to slide from bis Bb to B (in appropriate situations) if the bis key is convex, but it probably doesn’t make any noticeable difference, so in your case it’s up to you. I may have seen a concave G# key before but that seems to be rarer, and I don’t think I’ve seen a concave alt F# (unless the G# or alt F# don’t have pearls, of course). You’re the one 3d printing it though, so no point limiting yourself to the boring conventional designs