If you can build light, the AWX Edge will fly well on a piped OS 46. Ideally, and more simple, that ST90 you have would work pretty well, as will most any 90-100 4-stroke. All in all, the Saito 100 would make a rocket out of it! Mine had the Saito 125 and it was a rocket even at my 6800-foot elevation! Plan on 6.5-7 pounds with any of the aforementioned 4-strokes.