I didn't mention in my original post that when I talked to Yakima, they said that they would look through the back of the closet, so to speak, and if they found a set of 28V mighty mounts lying around, they'd mail them to me.

Well, Yakima came through - I got a set of 28V mighty mounts in the mail from them yesterday!

If you're in need of a set of mighty mounts for your factory cross bars, I'd recommend giving them a call and seeing if they'd look for a set for you too!

Good luck!