Wow! An answer from Sheldon himself - I'm honored!
Thanks... I knew I'd be increasing my risk of snapping an axle - but I'm a little guy, and I'd really just like to get a few more miles out of this wheelset with the parts I have on hand, so I think I'm going to take the gamble; I need to replace the freewheel anyway, and I've got the 8-speed just lying there in its box staring at me.... I *do* have a cassette wheel on order, though, so I'll be ready when the worst happens!
-chris