I have skimz SS18.0's on my 650g FOWLR with sharks, which has 3/4" glass. They stay put just fine until one of my sharks decides to knock it out of alignment. Doesn't fall off though. They're great if you need to push water a long way in particular.
Also have a Gyre. Great water movement and no issue on the glass, but mine is a bit unreliable (XF150- bought used)