You sound like your trying to figure out how to get closer to the "Advertised" speed of that Guardian, but it ain't likely to happen. And I'll doubt you achieve the BC speed either. I'd recommend setting it up the way it is "supposed" to be, using an arrow with an appropriate spine, and getting the FOC correct, and enjoying the bow, while not really worrying as much about the FPS.

Making adjustments that gain 5-10 FPS aren't going to change your trajectory that much, but may affect your bow as lightening the arrow results in a more traumatic recoil in the cams and limbs. As for setting sight pins @ 20 and 35yds, I found that with my set-up shooting mid 260's, I like 24yds, 32yds, 40yds, 48yds, and 56yds (There's a reason they allow 5 pins in that class!!!! You might as well get some good use out of them.). The 8 yd increments seem to put me in a position where I cannot miss SO far off that I don't still end up with a kill shot on whitetail sized game. This is how I set my bow up for hunting, and I use it the same way for 3D.