[EricH]

Sheet metal is as strong as regular metal that thick. However, it needs to be have its reinforcements. Flanges, support coming in from the back side, an extra layer, all that good stuff. This is because it's a lot less resistant to bending when hit from the side without those.

The reason you haven't seen the 1/8" tube bend or break is partially because the bumpers have been around to absorb the impacts. I've seen a couple of failures of that material, often around welds or stress points (say, somebody misplaced a speed hole). It also has bending resistance that the sheet doesn't (without the flanges).

And yes, 2010 was rough on drivetrains. The bumps hadn't really been seen that way for years. Plus, 148 was doing a drivetrain type that not a lot of teams had attempted before, even in 8-wheel form (they had 9 wheels).