Mine houses roughly 10-15 gallons plus 5 in the ato,,,,if it blows apart it will cost me close to 1k to replace the floor I put in 8 years ago in the living room,,,,,,,,,,,weld-on holds,,,,no worries. Just make clean straight cuts and use fast clamps to hold seams together for a couple of mins. If you have leaks when your done before putting project to use,,,easily fix the leaks with weld-on 16...
Ive done this a couple of times and each time Ive done it I worry I'm gonna do something wrong,,,,,,never had a problem though. 10 years ago when I built a sump I even routed the edges,,,it looked like it was factory made