On Monday, September 5, 2016 at 9:40:20 PM UTC-4, AS wrote:
On Saturday, September 3, 2016 at 8:34:50 AM UTC-4, wrote:
On Friday, September 2, 2016 at 11:02:16 PM UTC-4, wrote:
Ever known a suction cup mount (RAM) to mar or distort a canopy?

If surfaces are not clean eventually there will be a bit of dulling due to abrasion. There is not enough force in a cup the size commonly used to cause distortion.
UH

Tend to disagree! My new (used) glider shows a large (6"-8" dia.) circular distortion in the forward, flat part of the canopy, where a suction cup was attached - apparently over a longer period of time. Depending on the size of these cups, the force they can exert is considerable - certainly enough to stress and eventually distort the Plexiglas.
Assuming one can draw a 100% vacuum on the cup, a 8" (0.2m) diameter cup can exert over 3,000N (675lbs(f)!
Uli

So- like most answers, the issue is degree. I haven't seen a suction cup used that was more than 3 inches. I've used 1-1/2 inch cups for years. Go to 8 inches and, as Uli noted, it likely is a much different thing.
So the correct answer is "that depends".
CU
UH