Mike, I believe that I'm following your tweek of MixMaster's suggestion. I'll pull the YS out of its box and see what might work. Like I said, I'm not opposed to reaming out the flange holes. But the least work for me and least added weight for the toy the better for both.

Maybe I can build-up a small bolt like a 2-56 by sheathing it with multiple layers of heat shrink tubeing until it's the size of the flange holes instead of using fuel tubeing. It will be interesting to see how much the YS jumps around under the aluminum plates (or stainless steel). I'll need to make the test stand "a little flimsy" so that I can see how much vibration gets past the mount.

I just wish it were not so very cold in my garage. That's why I like to be glueing balsa this time of year! But then again, I have just begun this project and the only glue already applied is to the fuselage (which looks to be rather sturdy... wishful thinking). In fact this afternoon I was able to take the three bags of concrete back to the store and get my refund. I know... I'm a bad boy; but I did not have any other weights handy to hold the poly glue for drying! At least I actually returned them all the way to their original pallet in the store.

Whatever I end up doing about the engine for the 10-300, I look forward to adding this toy to my hanger for abuse next summer. I'm enjoying gas and glow toys so much that I may give my sailplanes and electrics to my grandson... lucky guy.

Thanks to all, and fly safe, Glover