I've moved to shooting almost all kinds of trap with 1oz of #7.5 moving a shade over 1200fps. For trap, even from the 16 yard line, I shoot Full. I've tried it with a more open choke and I never seem to do as well. A couple weeks ago, I shot a few rounds using a Modified choke, and ended up with one of the lowest scores I've had in a long time, and my best round was 23. Frustrated with that performance, I swapped back to Full for this week, and ran 49/50.
For me, I think it's a confidence thing. If I see the clays disintegrating into atomic particle-sized pieces, then I feel good about my shooting and continue to shoot well. If I see enough hits that leave chunks flying around, then I start wondering if I'm in the fringe of the pattern... which causes me to make adjustments and start missing.
That being said... I worked my way from Modified patterns up to Full over a period of months when I was starting out.