I have purchased a d-d reef pro 1200 which is yet to arrive (120x60x45cm). I decided to go for 2 ai Nero 3 power heads rather than a single Nero 5. I am concerned that it may fall off as the manufacturer says it is good for up to 12mm glass which is the exact thickness of the tank glass. Does anyone have any thoughts or experiences with this pump on 12mm glass?