I use 9s on all my PRS with great results, as long as they are coated, specially Elixirs and Mangans. Coateds are just a ted stiffers. I understand scale length plays a big role on tension, but I've been using 9s on all PRS for a long long time and they always felt "right" to me, no matter if it's 25, 24.5, 24.6 or 25.25; despite the fact I use 10s on most of my other electrics, either Strats, LPs, Teles and others.