The results are in. I left the backing on the acrylic, it didn't affect my cutting power at all, and there are no swirl marks. Yippee! :D

I'm cutting 0.090". My air assist is almost always on, but it might not be bang-on in positioning. At any rate, leaving the backing on works for plenty of reasons (swirl marks, scratches while bevelling, scratches during shipping, etc...), so I think my best bet is just to leave it there until the customer wants to install the thing.

Thanks a bunch, folks! :-)