I run a 3" diameter steel driveshaft made by a local driveshaft shop w/ 1350 joints. I told tem what it was going in and that I wanted something that would last. Not sure how thick it is or exactly what material....all they told me is that it is a "thickwall" tube. Been in the car since 2008.
8.95 at 149.7 mph at over 3900 lbs.

Not saying a 3.5" shaft isn't better, b/c I'm sure it's stronger. Just showing what I've done w/ what I have.