Stan,
Good job. I held short of recommending people use their hand as a temperature sensor. But a hand makes a great sensor if you don't scald yourself...at which point the exercise has failed. Bonded aluminum is an even greater risk, as epoxies and other bonding agents soften with heat.
It's pretty hard (but not impossible) to get into real trouble with a bonnet buffer. My concern is generally with turning-arbour wheel buffers. It only takes a second to melt aluminum with a cotton buffing wheel and brown buffing stick compound. Less than a second with black. You should use white with aluminum, but home hardware folks generally end up with brown, as white is usually only sold for commercial use. For some reason, home wheel buffing kits usually come with black, brown and red. They'll work, but aren't really the right choice for aluminum. Red is remarkably messy and really too fine for aluminum.
That said, you can wheel buff or bonnet buff even material as soft and delicate as plastic if you use proper care. It is just another of the many things you have to keep in mind when you meddle in materials.