I don't see why this tank wouldn't hold up to 75g of water without rims. Wouldn't the aquarium split in the corners if it was built poorly regardless of a rim or not?
I know my AGA 29 Gallon has alot of gap between the rim and the glass all the way around so it can't really be holding anything. Plus the pressure from that much water would snap the cheap molded plastic like a twig if the aquarium decided to pop.
of course you know what they say about opinions..