dpb wrote:
....
I'll note that since you have access to the joists, one way to
accomplish this is to occasionally where you wrap the tape around to
fasten one end solidly, then use a lag or even a bolt through the other
end and use that to tension the tape--it'll make a solid mount that
still has a little flex. ...

OK, since I've gone this far, I'll throw out another option I've used
that's simple and effective (albeit not usual for interior plumbing, but
what the hey... ).

Two wraps of #10 malleable wire (heavy fence wire works, well) fastened
solidly to the joists and then just tension w/ a twist. Will work
better in this case if the pipe is offset closer to one side so have a
little longer span for the twist, but this "trick" is useful for all
kinds of problems...

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