With rigid PVC you're then faced with the same problems as a soldered copper setup.
I don't think that there have to be structural concerns necessarily... as I understand the project these elbows replace any bends in the tubing, allowing for basically straight runs of tube. Just use lots of goop. Perhaps you could even fashion some sort of a compression ring that would fit inside the tubing and copper elbow?
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Michael E. Robbins
M.A.Sc. Candidate, University of Toronto
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