I can't comment on trap, but I practice skeet almost exclusively with 20ga. It hits practically the same with less recoil. If you're on, you're on. You may not get some of the chips that you'd get with the full 1 1/8oz vs 7/8oz.
I load Winchester AA hulls with claybuster AA wads, cheddite primers and Aliant Unique powder (7/8oz of #9).
Brad.