Just talked with the Al guy. He said the tolerances between the OD of the sleeve and the ID of the rail might cause some interference. He suggested getting 1 1/8" OD for the sleeve. That would give me 1/16" wiggle room all around.

The other option would be to get the 1.75" tubes long enough for a single section, 7' long. This ain't in their closeout bin and would cost $180 for the 4 rails. That compares to $110 for the built-up spliced ones.

Hmm...