Doubled 2x4 will do the job (Rally's 300+ is made out of those and it holds, i think a tank half the size will be fine lol). If you still doubt, then pay extra for the 4x4. Otherwise you will doubt everytime you look at the tank and that is not a good feeling haha.
Like said, peace of mind is priceless...
Like said, peace of mind is priceless...