Awesome idea! Thank you!
Well... some bad news/good news.
Bad news... One of the guys at work that works fiberglass all the time (makes boats and surfboards) said that while the tank was cool and congrats on the unique solution to a difficult problem... it won't work for fiberglass. He said the edges are too sharp for the glass to handle. I'll need to round the edges over somehow, or just make it out of metal.
Good news... I have several sheets of 2" foam left. I can make another tank form out of it and easily round over every curve and edge with ease. It will be a mess, but easier than welding that much sheet metal in this heat.
So that's what I'll be doing this weekend instead of glassing. Minor setback, but the way this build has been going, it's not really unexpected