Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
The bolts and feet idea that you have will minimize the amount of water under those feet, and any water that does get under will evaporate quickly. But that is a lot of weight to put a large tank on just 4 or even 6 of those feet. I would be concerned about denting the floor.
However, if you are using these inside the plywood box, then dents are of no concern, as long as they dent evenly, or you check and adjust to keep the tank level should be no problem that way.