built-in ballast or not??

I've got the floor of my 84 Supra torn up. As long as its torn up, should I be thinking about using some hard tanks to add ballast? The attached picture is what I'm dealing with, except I now have the gas tank out. I plan to put a seat/step across the back. I am thinking about a tank that goes along each side, and then one that runs the width of the boat that the seats cover up. They would all get connected to make one big 100 gallon tank. Problem is, where to get such an unusually shaped tank, or what to build one out of. Or should I just suck it up and have sacks sitting on the floor.

Ok, let's hear it, good and bad!

You have it torn up, go ahead and add some tanks. If you are good at glass work you could glass tanks yourself, or take it to a glass shop and have them do it. Or have custom tanks made and just cover some plastic wood in carpet to cover the old area, probably a break-even on cost. I think glass tanks would be cleaner butt...Good luck...Post Pics