ali you probly dont want to have all them sharpe corners, stress is just gonna build up there, put small rads on, as for being coated you could get coated with a process called tennifer (spelling)? which is what the do to forming tools to make them very hard, but im not to sure if it can be done on alu.
you could try as a start to get it heat treated and try that as i dont think your gonna get the same heat build up with trials as to down hill
and i dont see why they can made one from steal as you would use the same cutting tools just a much lower cutting speed :turned:
looks kool though and good luck with it