carefull with the cam software, you're going to fall in love with all kinds of cool stuff that will be a killer to actually make.
trying to drill all those holes over a lengh of round stock and have them come out the the exact same radial position would not be very easy, at least in the home shop. Here's a great web sit of one who did it, lots of good ideas there.
http://www.buildyouridea.com/cnc/IG-...phase_two.html
The next level up would be to consider buying the shafting, hardened and ground with the holes already drilled,m although you still should somehome have a V on the top of the support to give lateral strengh
http://www1.mscdirect.com/CGI/NNPDFF?PMPAGE=3872
while more $$$ it is a hardenshaft that will give better performance and wear
Finaly, for mucho's $$$ go with a linear assempbly like.:
http://www1.mscdirect.com/CGI/NNPDFF?PMPAGE=3873
they don't show them in 10' lenghs but you must be out there somewhere
imo you want steel rails over AL, and hardened is better still. With a mig i'd be all over making it from steel. Warping is controlled by the fact that you don't need an 8' bead, just some thing a little more than tack welds every half foot would probably do. I've always found Steel is fraction of the price of AL, and shapes like square tubing are readily available