jwottowa - I've been sitting back, watching this part of the forum as Gremlins are also one of my favorite planes too. So when you posted your question about reinforcing the engine mount I knew I had a photo to share.
I don't know what you're using to mount your engine, but I use 3/8 inch aviation plywood as in the picture. I've never had problems with mine. In fact the one in the photo has flown for almost 10 years the way it is. Although I'm not using the Jett 35 anymore (way too much engine for the Gremlin) any other engine, with this mount, and they seem to fly forever. Mike