Ok, I went to Lowe's with my digital caliper. Stood there and measured
various pipes. All of theirs was right around 1.050, where HD was 1.070.
So, I bought a few pieces. Took them home and had more positive results.

On my more expensive clamps with the spring plates, they worked great. On
my ebay specials (with the cam/teeth), some worked, some did not and some
would not fit.

So, I guess as long as you buy decent quality clamps, the galvanized works.
Also, take a caliper next time you buy pipe. FOR ME, it appears 1.045 -
1.055 is the sweet range.

dave