I tend to build all of my planes a bit on the heavy side.... (Can't seem to get comfortable with that "just a dab of glue" philosphy!). Anyway, I'm planning on putting an OS .91 FX on my Tiger Deluxe. What with me building heavy and the added weight of retracts, I don't think it will be outrageous. After all, nothing in the book says you always have to run full throttle, right?