But when it’s very windy, I only take one yagi anyway.
I usually use 2x5 DK7ZB on the 144 MHz Tuesdays. When struggling with the wind, I rather remove the upper antenna that is 6.5 m up the pole. The remaining “lower” antenna is mounted at 4.5 m and due to the larger diameter of the pole, she stands like a rock up to wind speeds the operator doesn’t want to take anymore.
Another issue is fixing the antennas in a certain direction. From experience, with only two arms it is annoying to fix the pole with one hand when you have to operate a station, hold the mic or key, and log the QSOs with the other hand simultaneously. The solution on how to increase the friction between the pole and its fixation is specific to the location. What works for me most of the times is either applying some foam (e.g. my insulated sitmat) between the pole and the velcro that fixes the pole to a structure like a bench, rail or fence. Or I lower the mast by two elements and put a conical Hirschmann Büschel Plug in the gap.
Developing a weather independant SOTA VHF station is a challenge and takes time. 
Ahoi
Pom