most cells like those made by RCI, Jazz, and Fuel Safe have a 20ga steel can.
I am exploring options because Id like to see what I can get away with to keep the weight down. The more I think about it the more it looks like A poly cell in a steel can is the answer. I cant have a unprotected poly cell hanging below the car. Any debris can puncture it. Aluminum is too brittle and prone to cracking. Steel has the best fatige strength and elasticity. I REALLY want to strip weight off this car but this doesnt look like the best area to compromize.