Above invitation applies to me, as well. I'd recommend looking at these fittings vs. the speedrail http://zebec.co.kr/english/accessories/Frame Parts.htm more $ but much better casting & come drilled w/pins. I have a source for pins @ $0.68 each (+S/H) for the 5/16" if you need those in any #. You should be able to get 6061 aluminium pipe for less than $3/l.f. for the 1-5/8" o.d. Remember to go with 6063 if you're bending it. Something you want to consider is the type of tube design once you settle on a size. Rocker-vs flat. You're going to have a more responsive cat with a rockered tube like Sotar at the expense of less carrying capacity than the flatter design like the RMR. Good luck and let us see it when done.