On 2008-04-09, George wrote:

I think they are called riser clamps. A real plumbing store will
have them.

Hmm, riser clamps are designed to rest on the subfloor or bottom
plate. So I'd have to nail some blocking onto the side of each joist
to give the clamp legs something to rest on. Plus with a horiztonal
run, the clamp legs would be flat, so they'd be loaded in their weak
direction. Seems like a bit of trouble butdoable, probably sturdier
than plumber's tape. This would be a good option if I can find some
extendable bar supports.

Thanks, Wayne