Yeah, I wouldn't be wrapping the clutch up either, think you'd be asking for heat build-up and accelerated wear.
Better to figure something else out....or ignore it. This is on a friction drive?
You state the rattle is louder than the engine, that don't seem right. I do think there is a certain break-in with the shoes and drum, but should resolve itself shortly.
Let me ask you this: with the motor off and engine channel raised, does the spindle turn freely without the drum scraping the clutch shoes?
The reason for asking is alignment. I've taken several of these things and swapped motors to different size spindles back and forth a number of times. When you bolt the channel to the engine it's necessary to get the drum centered on the clutch without scraping the shoes, cross-tighten the bolts a bit and keep checking alignment before snugging up the bolts completely.
If your clutch doesn't sort itself out, it might be possible it was assembled a bit out of alignment.
Or, you could try something like this:
http://motoredbikes.com/attachment.php?attachmentid=11328&d=1221538523