On Saturday, September 3, 2016 at 3:02:16 PM UTC+12, wrote:
Ever known a suction cup mount (RAM) to mar or distort a canopy?

It's not the suction cup that is likely to cause damage, it's whatever is attached to the cup that puts a twisting load onto that small section of canopy.

I had a heavy outlanding a few years back in a Discus (basically landed sideways and was lucky not to break the tail off) where the PDA/suction-cup caused the canopy to crack along the length of the mounting frame on that side. Yes, I admit that I never ran a 'control' experiment (by landing sideways without the PDA) and thus the evidence is circumstantial, but ever since then I've always mounted PDAs on the cockpit or instument panel.

You're probably OK with a small item on a short lever like a GoPro but I wouldn't trust anything heavier. Look along the outside of the canopy or look through it with polarizing sunglasses - if you can see any distortion then you're asking for trouble in the future.

My 2c.
DH
TX