I've been flying my WM Super Chipmunk w/YS91FZ about 4 months. Great flying plane! And beautiful in the air and on the ground. I used all the stock hardware which has been fine. I fly off a paved runway and at first had a lot of trouble with the retracts, bent struts almost every flight. Learned to land this plane a little better (keep the speed up!) and installed a new set. Now they are fine. Most of my flights were with the retracts down. I was afraid they might not come back down or stall the servo if retracted because of the bent struts. But with the new set I started flying with the gear up. Big difference. Plane flies significantly better, rolls in particular are much more axial. I like it even more.

Also the YS is a fine engine for this ship. Mine will go up until I can hardly see it, huge loops and cuban eights. I also have to fly with a little down trim, but it is no big deal.

Be careful handling the sheeting around the wing root, it's pretty delicate. Good luck, you made a good choice.