kevin - thanks, it looks like you have the us rack. i think im going to attempt something like this soon. (once i accrue a few more paychecks) i'll post my pics too once done. When i wen tot hte bike shop on sat. they had some newer designs, for instance yakima now mounts to square and round bars using same hardware. they also have a rear wheel (cup) its 7" or 8" long instead of the "sled" that i am used to.
emailed to me:
"The parts I used are:
A set of Yakima 14H horizontal mighty mounts $40/set of 4
A blockhead fork mount #1117 $20
A short wheel tray from an old rack ( you can probably find one of these at a Yakima dealer) A few 1/2-20 bolts, washers, and nuts
I attached the blockhead to the front rail with 2 of the mighty mounts and 2 bolts (Pic # 24)
I attached the rear wheel tray to the rear rail using one of the mighty mounts and the carriage bolt that came with the tray. The head of the carriage bolt fits into a channel on the bottom of thee tray and goes through the mighty mount and then a wingnut goes on the bottom. (pic # 21). Just be sure the bolt is chort enough that it doesn't hit the top of the car.
Another possibility which would probably work even better is to buy a Lockjaw bike mount Yakima # 2037 for $85 and mount it to the factory rack using the 14H mighty mounts.
http://www.yakima.com/products/dynamic/8003518_7.html
I would have used that set up except, I like the fork mount type and I had the wheel trays at home from an old rack and I was too cheap to spend the $85 dollars.
I want to be perfectly clear that the 14H clamps are not made for the Mazda rack but I find that they fit pretty well. Also, I make no guarantees as to the integrity of this set-up. I suspect that the roof rack is the weak point in the whole system. Check the T bolts to be sure the rack is secure. I also have been checking the mighty mount clamps for signs of fatigue and cracks. I have had them on since August and so far I have seen none. I hope this gives you some ideas.
Kevin"
pic the first
pic the second
pic the third