Thanks for the input Jazz. I totally agree with the proven L shape being stronger per $. I'm not too worried about setting it up as the whole thing can be bolted together and adjusted before welding BUT I only have ARC. A bit of bowing of those tubes is not going to be the end of the world but if I get twist its going to be a throwaway so I'm seriously reconsidering my options. I can't get any square tube with walls thicker than than 3.5mm at my local steel shop so that's another curve ball I have to try and dodge with whichever design I'm going.

>>Also Please don't tell me this is just for cutting wood with occasional aluminium use.?

Yes, but I also want it gentle enough to cut little harts on pink mash mellows and then maybe the odd piece of brass in between :-)