I have not heard of the issue you describe with the WSO100. I would contact Maretron directly for questions on that and then let us know. ;-)
My plan is to use a piece of Aluminum
6061-T6 Bare Extruded Rectangle, 0.375" x 3" x 24" (aka flat bar). One one end of the flatbar I matched the hole pattern for the bolts and humidity sensor on the bottom of the WSO100 so I can through bolt from under the flatbar into the base of the WSO100.
The other end of the 2' piece of flatbar will be bolted to the masthead.
I have the flatbar ($10 from Online Metals
which is local to me in Seattle) and drilled the holes, but my spars are being painted now so no installation
as of yet.