Well, I can't say whether a 1.5" OD tube will work because I can't find 1.5" tubing. The closest I can come is 1 and 5/8 and no, it doesn't work, too big.
However, I looked at the photos provided by FlyGuy and did some thinking and I think I have a setup for blowoffs that will work like a charm AND be easy to clean. I couldn't find a parts list for what FlyGuy showed pictures of but here's what I bought and it appears to work.
10' of 3/4" PVC
1' of 1.25"OD Tubing
4 3/4" PVC Elbows
A pair of PVC cutters, the ratcheting kind (This isn't necessary so to speak but a hacksaw leaves a much rougher edge.)
For my setup I cut a piece of the tubing off that was about 2" long. Then I cut three sections of PVC, 6", 10" and 22". Stick the 2" tubing on one end of the 6" piece, it's snug and you'll have to work at it but it will fit, and then shove that end into the carboy. For me, the fit was tight enough I could pick the carboy up by the 6" PVC. Connect the 10" to the 6" and the 22" to the 10" with the elbows and WHAM...you're done. Parts, including the cutter which was $12, cost me $17.
Thanks for the tip FlyGuy and I'm really looking forward to my double-brew day tomorrow.