I agree. The shape of the VP9 (and P30) backstraps is a mistake. Ergonomically, it and the side panel adjustments might feel great to hold. Performance-wise, however, they are a real problem. It leads to inconsistent recoil control. Namely, the curved shapes from the backstrap (not just the back of it but also the flare mid-way up the backstrap that flares out and curves towards the side panels) cause follow through under recoil to be erratic. Instead of the gun recoiling straight up and down, you end up with an inconsistent figure eight pattern style tracking of the gun under recoil. Is it the end of the world? No, they're still phenomenal guns. But it is damned annoying.
The relatively square and slab sides of the USP, USP Compact, P2000, and HK45C are much preferable, IMO, and generally more consistent for tracking under recoil.
No one currently offers alternative backstraps that solve this problem. A few companies, like Taylor Freelance, just mimic the same factory shape. So what do we do? Although I haven't tried it yet, one potential option may be to take a factory backstrap and build up a substantial layer of epoxy on it, then grind it down to change the profile. I have experimented a bit with taking a large backstrap and grinding down the flared sides to better match with medium side panels, which did improve the feel a bit. I haven't tried to grind the hump on the backstrap yet though.
Thankfully, the VP9A1 grip redesign was, IMO, a big step in the right direction. Namely, removal of the finger grooves and some of the spiderman curves such that 3 of the 4 grip sides are now a more consistent rectangular/oval shape with fewer weird contours. The backstrap is still a problem. Though, for those of us with larger hands, the new extended backstraps with the beavertail are an improvement in trigger reach at least. I have a large extended on the way for my gen 1 VP9 ("VP9A0" or whatever we're calling them lol) and will probably play around with grinding on it a bit. If so, I'll try to get some pics.
