So, short version - I have XL+ hands give or take, and I'm finding that certain firearms/grips leave me at the point where my support hand isn't making contact with the firearm at all...which means recoil control isn't all that great.
An example of this - a Beretta PX4 Compact with the large backstrap and grip tape on it; if I grip it with my strong hand firing grip ready for my support hand to meet it, if I take a dummy 45ACP cartridge, I cannot grip or squeeze it in the space between my index and ring fingers, and the meat of my thumb. I can't even orient them in such a way where that's possible; there's plenty of support hand grip space available on the gun for the support hand to make contact with the grip/frame without needing to move anything on my shooting hand.
However if I try this on a CZ75/P01, I can very easily take control of and pick up a 45acp dummy by squeezing it between my strong hand middle/ring finger and the meat of my thumb, while in a shooting grip, without adjusting anything. Since my support hand isn't made of silicone putty, it basically never touches the grip/frame...it just can't really squeeze in the tiny amount of available grip space on the support hand side of the gun. Not unless I back the rear of my shooting hand off the backstrap a bit to let my support hand wedge in and make contact with the support side, which is what I wind up doing.
On a 1911 with a flat mainspring housing, I can grip the dummy 45 with a slight shooting hand adjustment; with the arched mainspring housing, I can only grip it if I mess up my grip a lot. Same with a Beretta 92 (NON-Vertec); it's only if I deliberately crowd the frame into a grip I wouldn't normally shoot with that I can pinch the 45 dummy round between finger and meat.
Anyway - the reason for this - I bought the aforementioned P01 ages ago; I like the CZ platform, I like that it's a decocker without a thumb safety; I like that it's G19+- sized with 14+1 (or more depending on mag size); I like that it's millable for an optic; and I like that you can mount a light to it. I spent a good bit of money on CGW bits and making some improvements to it like sights; DA pull is around 7.5 pounds and SA is a mushy 3lb (which is fine for me, I'm not shooting this in bullseye). I found though that whenever I took it out for practice, it was pretty difficult to keep total control over it; it would move around a lot under recoil...because the rear of my shooting hand was backed off the backstrap so my support hand could make contact with the grip. I also found that often after a few mags at the range, my support hand kept just slipping off no matter what I did since there was so little real estate for it to lock into on the gun.
Am I overthinking this? Is this something I should just work/train around, or is this something I should actually pay attention to and try to fit things to me, vs fit me to things? I've been trying to whittle down and remove things that I just can't make work for me, but there's this nagging voice in the back of my head saying 'Don't sell this stuff, it's a "you" problem and not a problem with the tool'..
Visual examples (all firearms rendered safe before photographing):
PX4:
CZ P01: