Yeah, I know... It does'nt suffer from the same water pressure that the top rim of the tank does by any means, and the silicone at that bottom seam is hogged on there for a pretty strong joint, but the worry wort in me (and the perfectionist nutter) would never let that sit...
I am sure you will be fine, especially since you got word from the manufacturer to that effect...
Just curious, did they ask for photos of the damage when you asked?
Just to let you know, Gorilla Glue is a polyurethane adhesive used to bond porous wood together, and although it is water resistant and may appear to bond to glass and ABS plastic at first glance, indeed it is not... You would have done better to hog 100% silicone in there, but even that won't adhere to the ABS frame permanently. It will stick like the business to the tank though.