Thanks for the good replies guys. It is possible I might be over tightening them. All I'm using to tighten them though is a nut driver with a screwdriver like handle. Still, #6 is not that large and I could be over tightening them. Hey, an idea though - when I get home and am cleaning the plane up I usually check the engine mount bolts for tightness and find they usually need about a 1/16th turn or so after flying. Maybe I should just leave them alone. Another thought is that I am not putting a washer under the head of the socket head bolt where it goes into the Saito mounting lug. A washer might soften the vibes on the socket head. There might not be room for a washer though, will have to take a peek.