Be sure to use DOM tubing. Sch 80 & 40 may be good enough but it is a welded pipe (weak spots). I have always heard that tubing is recomended over pipe. I used 1.75-.120 wall. This is what they use to build stock car frames. Again these are things I have been told by other wheelers/builders. If you go with 2" you may find it hard to get someone to bend it for you. I took a 20 foot length to a muffler shop and had them put a series of different bends in it, then I just cut out the angles & welded them In as I built the cage. Worked out great & had plenty of options.