Hi Mike,
i've built and flown the Saphir (.60 size) and it flew fine with an OS .61RF-ABC-P (If I'd had a Hanno special I'm sure it would have had more vertical!!). I have the Saphir II 4-T kit. It was designed around the original YS 1.20SF. 70" long and about 950"sq wing (mine is still in the box).
I saw Wolfgang fly the original Saphir (.60size) modified to accomodate the YS 1.20 at the 1989 World Championships. It was a rocket - it appeared to acclerate in the verticals; power was not an issue! Ironically, Tony Frakowiak flew the Fyg Leaf biplane powered with a YS .61LS at the same contest and it was the slowest airplane there. Both pilots flew well, but the difference in maneuver size was amazing!
One last tip, if you use retracts, make sure the retract plates are well anchored in the wing - to something other than just the foam! I made plywood plates running vertically from the top wing sheeting to the bottom and glued the LG plates to them.
Happy flying - love those funky wing/stab tips!
-Will B