Hey guys,
I used "super strut" I call it Uni-strut. I'm an Electrician and I use it all the time for extremely heavy stuff. I've hung transformers on it that weigh upwards of 300lbs and have never thought twice about it. And as far as hardware for it, 3/8 is most likely plenty.
http://dodgeram.org/tech/specs/bolts/SA ... ength.htmlIf you show me a rough diagram of what you're planning I can tell you where the weak points are too. Just so you know they make 45's and 90's brackets for supporting your center riser if you're doing a single column gravity system. Yes, you will want spring nuts and I do recommend square washers instead of flat washers. They're thicker than flat washers, try top make the bolt the weakest part in the whole set up.
I'll try to post pic's of mine. It'd too easy.