Anytime. I wish I could say the same. My Chumba weighs in at just under 30lbs, I don't even have a clue what the steel rigid 29er weighs (nor do I want to know hahahaha). I can say on a windy say I have dropped the 29er on the roof after riding while trying to get it up there.
I think the factory rails (not crossbars) are also rated at 100lbs (there is a sticker up there on mine that saids that, not clear on each or total). Since the aftermarket crossbars essentially clamp on to the rails you can possibly run both, but the clearance for the bike tray might be compromised and probably will not work, but I think they should work. Find someone locally with aftermarket crossbars on iS and ask them to try it out.
I can say that into the triple digits the roof rack works well. So if you choose that route it'll do nicely.
I haven't been riding at all in the last 3 months. School was keeping me busy and now I am studying for a board exam so that'll probably nix any riding for a while.