Mine is currently skinned in some heavy ass 1/8 thick aluminum. I will not, errrrr, should not be able to destroy them. 4x10 sheet of it was right at $200.
4x10 sheet of 1/8 Lexan is right at $100 here.
I also have some tin, seriously a roll of barn tin bought off the Amish Barn building family in the LP Michigan. $20.
Each has benefits and draw backs.
Barn tin, easy to cut, easy to attach, easy to destroy, not as easy to paint and look good. The pics of mine with the grey and red skins were this barn tin. Cheap and pretty nice.
I destroyed one skin though on the interstate. Wind hit it just right and peeled it like a banana then whipped it until it beat the piss out of its self. I still ran it two more wheeling trips. It had character.
Lexan, more expensive, you have to actually take your time cutting. You spray paint it from the backside and it looks good. Scratchs, and generally attracts dirt IMO (Static?). But what I really hate, once its all bolted on, anything and everything that hits it sounds like a snare drum. It rattles like a drum. I hate the noise!
Thin Aluminum or the 1/8" I've got on now. Costly but light for what it is, 1/8 hard to destroy, and has enough ass to it not to rattle or flex and sound like a soda can. Down side is cost and it wieghs more than barn tin or lexan or thinner aluiminum that would be easier to tear.