I apologize if this has been asked and I missed. I just spent the evening going through 29 pages of Forum topic lists looking for the answer. I did find a lot of topics I need to keep in mind as I build. I am planning to put a Corvair engine in my Kitfox 5. I am not sure what the weight comparison between Rotax engines and the Corvair is. There seems to be a lot of opinions. I need to know if my engine mount bolts will hold my Corvair satisfactorily? On my 5 the top 4 bolts are 1/4 inch and the bottom center is 5/16. Does anyone have an O235 or O200 flying with the stock size bolts? If anybody has one flying with this size bolts I can go ahead. If I need to upgrade my bolt size to 3/8 I can do that work as well. The fuselage came with these bolt spools as far as I can tell. They have the very good welds I have found all over my Kitfox fuselage.