The sides shouldn't be tempered. You could connect them with a 6" clear PVC pipe tunnel!, Get some big time bulk heads, and find a 6" hole saw!
At the very least, you could set them next to each other in whatever config you like (L shaped, end to end, side by side), raise one up 6 inches, then drill the upper tank develop some clear acrylic spouts to put in the hole, and rig a canister filter to suck water out of the lower one, and pump it to the upper.
I didn't realize the sides wouldn't be tempered... I'm going to go do the LCD test, I really wanted to see if that worked anyway.
Sent from somewhere unknown to man...