A few thoughts...
Folks may or may not have noticed you have an aluminum frame, not to worry - I too have one lol but I did want to say that while it seems like a great idea, lining the motor mounts with rubber can actually increase
the amount your engine vibrates - although you will feel it less as its dampened a bit between the motor and frame.
On a steel bike... *shrug* perhaps people can get away with it tho I had fuel frothing problems - the big problem is that with using exhaust clamps as motor mounts you stand a good chance of crushing your frame tubes if you torque them down on a aluminum frame, add to this the problem of cutting/wearing through the rubber due to vibration & time and the chafe of the steel on aluminum and you might have some cutting issues...
Yet exhaust clamps make great mounts! Somewhere on the forum someone made a perfect and cheap mod that alleviated the above problems - but bedanged if I can find the pics... It was easy enough tho - they simply took flat stock prolly 1/16" - 1/8" thick, cut 1 - 1 1/2" strips outa it and bent them into U-shaped plates to go between the clamp and the frame and welded them to the U-bolt to keep 'em in place.
This spread out the clamp's compression, allowing the clamp to be tightened enough to stop the motor's wiggling (and the chafe prob) without risk of kinking the aluminum frame.
Aluminum bikes are awesome and I like yer build - but be so very careful about drilling holes and any movement at all
, I've had some chafe/cut issues with mine, even a rattling chain guard had nefarious thoughts, keep an eye on yer bike and all should be well though
Some additional tensioner ideas;