Hi, I'm very new to the forum and am curious about the pitfalls of building a height extension for my tank, I have a 20 gallon tank and want to build (using marine plywood or starboard) a vertical extension, using the tank only for the below water level and the lowest land portion of my paludarium. Basically to extend to an overall height of around 30 inches from it's height now of just over 12 1/2 inches, what kind of complications do you think I would encounter? I'm basically going to build it as an insert that will slip down into the tank being just under a hair less than the inside dimensions of my tank, the insert will need to be removable but sturdy, and I know waterproofing will be important for the base, and any part that will be in contact with the inside of the tank. Thank you for your help and positive criticism in advance.