I built one of these (English Yoke type) and found that it had a lot of sag. No, Bob, I didn't quantify the sag. but could see it in the eyepiece. I did not have benefit of the S&T article and probably used too small a tubing for the telescope. Taking a cue from the Porter's Folly mount I solved the problem by filling the pipe with cement. It was a lot stiffer, but a lot heavier, which may defeat the purpose of most who would use this material. -Rik