Have anyone tried to find a source of mild steel tubing (w/thin wall) to use in mock-up projects instead of using up expensive 4130? It seems what is available is either called mechanical or hydraulic tubing (the process difference between the two is normalizing). the tubing is SAE 1010 (10% carbon), so welding should be okay. I received a quote of $105 for a 20foot length (1/4" dia, .035" wall). That's no better than 4130, but I'm still looking.