Thanks. I saw the little nitch but it was still pretty tough. I ended up squeezing one side of the suction cup into the hole by the nitch and kind of used a pencil to pull/push the rest of it through...I don't think I will be taking them off for any reason. But I have to say, this is a great heater. It has a good modern appearance and an easy to adjust knob that does not appear to be able to be moved by an animal. The temperature has been steady so far.
When I got my heater I spend half a day sticking those suction cups in.
I ended up getting them in by forcing them in with a pen. The anger helps too, because you have more strength to get it in.