Sorry I didn't make myself clear but that is exactly what I have been proposing as two stage seal, seams then inside seal. The only difference and the fly in the ointment, is the flip up of the side panel with the chipped bottom, which must be removed at the same time but glued in first and allowed to set up enough to help support the bottom panel for gluing. I may even have to install a new inside bead on the flipped panel temporarily to provide enough strength and stability for the bottom panel install. Then after the bottom is cured and supported by steel framing, go back and remove all inside tank seals old and new for a clean wide one piece bond and seal.If you weren't removing any panes of glass all you would need to do is remove all of the silicone from the inside of the tank with a razor blade, clean with white vinegar and then reseal. As you need to replace the bottom of the tank i would silicone the new bottom of the tank on (i would have the tank upside down for this), then remove the silicone from the inside of the tank and reseal the tank (using a generous amount of silicone in the corners of the tank).