i don't think ur supposed to use 4 fingers - use index for both

Then I suggest playing Warhawk. Even better, try flying in Warhawk. You'll need your two index fingers on L1 and R1 for the machine gun and primary weapons, and middle fingers on the R2 and L2 to be able to control your speed and mainly, power slide. Even if you only want to speed up or slow down, you'll still need two fingers on L1 and R1 at pretty much all times. 

Yeah, and you get used to it if you have to use 4 fingers for all R and L buttons.  The last game I did it a lot in was Twisted Metal because I believe R1 was machine gun and R2 was special.  I wanted to always be shooting the machine gun. 

i always use middling fingers on R2 and L2, because it feels more natural.
putting index fingers on L2 and R2 never felt comfortable for me.

Index finger for both

I have my fingers wrapped around any PS controller I've ever used, and my fingers never rested on the shoulder buttons. but if you must, rest on l, r1

I think it's most comfortable when put in a 360 shell.

 Just remember... Front to back, unless you don't mind getting a lil stank on your sack.

I always played with a finger on each. Seriously, I didn't think my hands were especially big, but you guys must be gorillas. Have you tried the Xbox controller?