Yes, those are all points I've considered, although I don't know much about the scotch yoke wear charachteristics as the only other place I've seen it used is the Bourke engine and there isn't much information about that. You do seem to have missed what I think is the most unique feature of my engine, the fact that it fires on both sides of the pistion essentially making it a one stroke cycle engine. The reason I think this is a good feature is that it allows a small engine to produce more power and do so at low RMP. But like I said before I really want to learn to fabricate, and if this engine doesn't work out I'll still be into metal work.