Re: Secure mounting.
Fully Agreed... Massdrive does mae some excellent quality stuff... not only mounts, but those mounts look great too.
Please, whatever you do, do yourself the favor and take it from those of us who know better... do Not use any rubber padding between the engine and the mounts... it's just disaster waiting to happen and the engine will vibrate the whole bike to death.
Solid and rigid is the way to go. When you get your engine all mounted up, you shouldn't be able to move it in the frame by pushing side to side from the cylinder head, if it can move, you'll need to make it more rigid somehow, whether it's by using a set of mounts like Massdrive makes or welding tabs and brackets for your engine to bolt directly to, the more rigid you can get it, the better for your bike and the less vibration you'll feel at the grips and on the seat.