I agree the PVC pipe method is probably not the best method for the 1.0m and 1.2m channel master dishes. In fact, I believe I've stated this before. I don't have a 1.2m but I do have a 1.0m and while the 1.0m mount attaches to the same size pole, it's much heavier, made of thicker less flexible metal, and made a bit different that the mounts used on the smaller oval dishes. Therefore, I completely concur that the PVC pipe method is probably the less desireable method with these dishes. I still like the PVC pipe method better for the smaller oval 40 x 30 dishes though as it's easy and makes for easy declination adjustment.
Also the Stab motors may indeed be a much better choice for these dishes. The reason I choose the SG2100 for my 40 x 30 oval was I thought it would be sufficent for this dish, it was cheaper, and I've heard it has a wider range of travel. Also if there are ready made adapter rings then I'd say definitely go with that. When I made my mount I hadn't seen any such adapters. So, I had to come up with something on my own.