I got my holes plugged today. I used a new, flat tip on a soldering iron to melt the plastic. I used a clear polyethylene bag as filler material. Heated up the area of the hole then used the soldering tip to mash some of the bag material into the hole. A little more heating of the whole area to smooth things out and I now have a leakless water tank. Total cost to repair - nothing excluding my time. Now I just have to figure out a way to keep the tank from moving around to prevent a the problem from happening again and I'll be all set.