Update on previous. GWVTs post got me intrigued.
So playing with my thumb riding 1/2 of a rail width higher (along the top edge of the rail), I found that my pinky finger, first section past base/1st knuckle -- between first and 2nd knuckles, 1st section from hand of pinky finger -- is what pressed against the rear of my AFG.
In my usual configuration, it's the 1st knuckle (a little) and meat of hand (mostly) that impact that point of the AFG.
Both, it's the leftside bottom edge that I'm pressing against, it isn't square onto the rear (right handed shooter, so left support hand is what grabs here)...
When trying to hold the weapon with just one hand, my support hand, on the foregrip, it's perhaps best described as trying to carry something heavy by squeezing the side (higher grip) or having your hand underneath (my standard grip). With higher grip, I find myself tilting weapon ~45* (12 oclock to at least 10:30 or so) to the side to bring back to a similar orientation to my standard grip due to strain... Standard grip, I find myself tilting it only ~15* (from 12 oclock to less than 11, 11:30 or so) to the side after awhile one handed to bring my support hand centered beneath weapon weight...
Considering above, I think I'm sticking w/ what/how I'm currently setup.
And for what it's worth, I have longer/large-size length fingers but medium sized hands and typically prefer medium sized gloves. I also prefer a tight fight w/ gloves for maximum dexterity -- and with good leathers a tight fit is critical for them to properly fit your hand once broken in... Mechanics, other off the shelf work gloves, etc, I grab the mediums 8 or 9 times out of 10... Offhand, I have some heavy winter goretex snow gloves that are large, but that's about it.
EDIT and NOTE: FAB's PTK angles most certainly are different than the Magpul AFG -- this is just what I've found w/ the Magpul AFG based on where I'm indexing my thumb... And this is w/ the NEA rail setup.