I'm TOTALLY inexperienced with this sort of stuff as I'm still working on the emp. Here's what I found works for me, though...
If I have the pressure turned up to 90, the trigger's really hard to control. As the squeezer pushes away, it's really tough staying straight with the manufactured head. I found that as long as I stay straight with the manufactured head the shop head takes care of itself (YMMV...this is what works for me). So I turned the pressure down to about 70 psi. My squeezer really doesn't seem to care what the pressure is....I have to squeeze most of the 1/8" rivets twice anyway with a 1/4 turn on the adjustable set to finish it off regardless of pressure....maybe I have a crappy squeezer...I dunnu. I just do a whole line, twist 1/4 turn and finish them off...it only takes an extra minute or two. With the pressure way down, I can feather the trigger to where i'm just touching, make any last alignment adjustments to the squeezer, then go to town.
Once again, this is just what happens to work for me.