If you can do this yourself, consider using 5/16" shoulder screws.....available at any industrial hardware store or Mcmaster.
When I did my roof transplant, the holes in the crossbars were quite worn (egg-ed out), so I drilled them out to 5/16" which made them round again and allowed a larger bearing surface area with a 5/16" shoulder screw.
Even if you don't go bigger, use shoulder screws, the stock SMB design is clearly under designed as many pivot bolts have broken. Having the tubing bearing on 1/4-20 threads is a recipe for broken roofs.
The repair should be very straightforward if you are reasonably handy; pop the top and stick 2x4's in the corners to allow you to work with unloaded crossbars. There are a few other very cheap upgrades that you can do like much beefier nylon spacers if you want. The shoulder screws need to be either 2 1/4" long or 2 1/2" long I can't remember.
Install the screws with the nuts inboard so they don't rip your canvas.
Here are a few pages from my thread showing the new hardware:
http://sportsmobileforum.com/viewtopic. ... 4&start=15
http://sportsmobileforum.com/viewtopic. ... 4&start=45