Indeed, 2 middle fingers are for the grip. The pinky and thumb can touch but dont do anything
I use quite a loose grip too. I actually shot 360s ex 400 with my pinky nót touching the grip of my Tau 7; a real sin
If you have one of those Free Pistols, your pistol kinda hangs into the grip; you barely have to grip it.
I also noticed that grip preference may vary per pistol. Especially with springer pistols but can vary with match pistols too