A 125-gallon tank will have glass that would be able to withstand 15.5 PSI. The tank weighs around 255 lbs empty, so yes, if it's laid on it's side against a solid object sitting on a solid flat surface, it will easily crack.
Personally, I wouldn't risk it on any tank that size. I think moving a 10-20 is fine, but 125 is getting pretty dicey, imo. I'd rather cover the whole area and not worry about drips, but that's me. Drips can be cleaned up with turpentine and a rag if need be.
If you are able to carefully place it on it's side on a completely flat surface, you should be fine. I'd use 3 or 4 people if I had them handy to avoid putting undue stress on the glass or seams, assuming I had to move it, but I again, considering it's overall size and bulk, I think it's a risk I'd avoid.