fairly avid welder here, i have welded up a couple of 14' rails and one 2' x10'x 2' high box, no pics but i can say that if painted and taken care of properly they perform and last a lot better then alot of wood framed items. i'll try and get some pics when i can
what are the specks on your tube? OD? and Wall thickness? I used fairly light tubing for the structure and a heavy tube for the actual rail, it held up but i had to use larger gussets on either side of the vertical supports.