team mate, on emay, or xbox website, of drill the frame an blot right through it
Here is my more coherent experienced advice on engine mounting.
Never EVER drill your downtube for the front mount regardless of what it is made of.
Just trust me on this, or just think about how sturdy a single bolt going through a flat plate and through a round pipe is going to be against the lateral and twisting forces of a gas engine!
What is the exact diameter to the 1/8" of the down tube on the Cannondale?
You can't just put a ruler up on the side and eyeball guess, this is crucial.
If you can't look it up and don't have a caliper just wrap a tape around it and divide that circumference length by Pi for the diameter.
A simple muffler clamp for your diameter (probably 1 1/2") downpost and you have yourself nearly 360 clamping power with side bolt tube support and a flat mounting surface to mount something flat to.
Muffler clamps are like $1.50 at the auto parts store.
Then all you need is a flat piece of medal with 4 holes; a set to match the front motor mount holes after you pull the studs out, and a set to match the muffler clamp U bolt holes.
The thing is the chances of just a flat piece of metal is not going to be perfect.
I found the best and easiest way to do a front mount right is pull the front studs out to start with, and then do the back mount first and forget the front.
Your seat post takes all the engine force to the back wheel so it is extremely important the engine mount is completely flush with the seat post at a 90 and secured.
Take this time to get your engine as low as you can, check your chain length to the back wheel... In short get the engine and drive perfect that particular bike, then fashion a front mount.
On a typical beach cruiser you will find the engine is too low for a flat piece...
... Or too high for a flat plate.
I build for a living and just keep SIckBikes universal mounts in stock.
http://www.sickbikeparts.com/catalo...ducts_id=74&osCsid=4en1gfuik5osnlpmeal2m6f3b4
It's a clever Z plate design to change the mount distance to front bike mount, it can be mounted above or below the engine and comes with all the bolts and some cool spacers for really far away mounts.
Hope that helps, I'm off to prep for the Super Bowl ;-}