Grrrrrumpy, Now the YS 91 may be too much motor!!! Just kidding. Watch the stock blind nuts in the firewall if you use them. Mine broke off at the flange the first time I went to the 16 x 4W on the 100. I was able to modify the stock mount a little and get the 100 to fit, not sure if the YS91 will or not and I'm not home to be able to measure it. Firewall must be strong, I ain't ripped it out yet. Did blow the horizontal stab off on both sides practicing roller coasters, patched and added 4/40 rods as braces to the bottom side and everything has been fine since.

The good thing about a 4 pitch prop on this plane is it keeps the speed to a reasonable level. I think this plane will self destruct if flown fast, but several folks are proving me wrong.

Ed M.