[Tom Wesenberg]

I agree with Farrell.

And, not only that, but you still can't sandblast the bottom where the holes are drilled, unless you have some kind of blaster that shoots backwards.

I would never drill or cut open a tank. If it had enough rust to be a problem that couldn't be fixed by flushing and using the small tank filter, then I'd use molasses to derust the tank. My next choice would be to buy another tank.