Answer
Jun 19, 2024 - 10:11 AM
The 39H MightyMounts are specifically designed to work between Yakima's CoreBar crossbars and their JetStream Crossbars(via a rip-off tab within the mount). Yakima has always been very studious in their specifications as they roll out testing on these products; and from the information I have at hand, it looks like they've never tested these on Wheeltek crossbars in general.
To help with the ever-evolving range of crossbar styles that the future may hold, Yakima created a new adapter called the Universal MightyMount(Yakima link, here, if we're out of stock) in 2005; and with it, they discontinued working on any new iterations/testing of their older, numbered, styles(outside a select few like the 39H).