Roger,
Question, are you attaching the iFly to a Plexiglas window. Something you might try is to find a smooth surface, mylar tap, wide clear tap and attach the suction cup to that. Plexigalss is porous and especially so if it is crazed the slightest bit. I wouldn't overlap tape or anything as that will provide an out or leak for the air.
Maybe double side or permanently stick a piece of round glass for a mount. I have not heard of the suction cup letting go of glass. It would be a great experiment non the less.