My Northwood Fox Mountain has a 2"x 2" piece of angle iron under the tank spanning from the frame sides attached with 3/8" bolts so it can be removed if you need to drop the tank.
While it only holds 54 gals I've traveled all over with it full. If I were to buy another trailer, the 1st thing I'd check is how the tank is fastened. We dry camp a lot so it's important that we carry water with us.
Any MFG that says their RV shouldn't be towed with a full tank of water or grey or black stuff is not getting my business.
