Can I slice off some of the plastic on my motor mount so I can mount the engine with the supplied bolts. They are 1" long bolts and BARELEY make it through the motor mount and engine mount. What do you think? Should I go buy new bolts? BTW I had the OS 51 Surpass on a Piper Cub and the mount was thin enough to use these bolts in..

I'd just head to the hobby shop or hardware store and get some longer bolts. You could probably get away with trimming the mounts but why even take a chance when some new screws are only a buck or so?

Amen, buy some longer bolts.

DaveB

As an alternative, and in the future, you can always drill and tap the mount. Then you don't need the bolt to go through for a nut. This works really well on nylon/glass filled mounts. Just drill, tap, harden with CA and you are set. No nuts to worry about.
But, of course, if you have already drilled the holes big enough for the bolt to slide through, then it is too late to tap it.

I buy these self-starting hex-head screws that are made of stainless steel at the local hardware store. I make a starter mark where the engine is supposed to be on the plastic or composite mounts (not steel or metal, obviously) and then attach a nut-driver to my variable speed reversable drill, and then put the screw in the mount and hit the drill. It startes then screws the screw into the hole it just created and then I'm done, all in one operation. It is tight, secure, and easy.

The bolts I am talking about are these: