Ok, here's my take on the whole Stormtrooper/Clone thing. In Lucas' mind, the Stormtroopers are now clones. They weren't in the original film or trilogy. The head bumping was a total blooper that Lucas is now working into the story. It is clearly an attempt by Lucas to alter the OT to better fit the PT.

As for Leia's 'short for a Stormtrooper' line, I had always viewed this as a joke and a put down. Trying to use this as a means to prove that Stormtroopers are clones is (at the very least) reaching or simpy trying to read way too much into something that just isn't there.

That's my two cents.