Interesting question for which I will try to remember my i12s experience. The main difference may be my stays formed a wider tripod so when a mast is forced sideways there is a little less upward leverage exerted on my gluepads than yours. I rigged the stays to have light tension to reduce strain on the gluepads. Maybe these pads don't need babying, but anyway it seemed to sail better with a surprising amount of slack on the leeward stay.
As for mph, I am thinking I coped with a couple mph above beaufort 4 which would be 15 gusting to 20, if the fetch was limited to avoid max waves
https://www.stormfax.com/beaufort.htm . Sustained as opposed to gusting 20 was only survivable by letting out sheet to spill wind or turning into the wind and letting the sail flap like crazy. An odd thing is if I tightened down the sheet and pedaled straight upwind, the sail seems to retain some drive. On a downwind run it is hard to spill wind and you may want to make extensions to your sheet or replace it with longer to reduce overpower.
Best to explore higher winds only in stages so you have a margin of safety until you know the issues. I never experienced a flip over, but had a few scares when a big wave and gust hit me at the same instant. I have practiced reboarding the yak at sea and lanyarded everything down including the mirage drive, paddle, and gear. Some find the sheet tension hard to hold in moderate to high winds, for which there are a dozen mods with their own pitfalls we could discuss. Don't forget to keep the fins vertical to avoid sideslip when not pedaling (pedals side by side gives vertical).
P.S. One issue with higher winds may be that you weathervane into the wind more than your rudder can counter. This can be reduced by raking the mast forward altho your boat may have limited ability to do this due to the small offset of the forward stay gluepad. Maybe I misremember and had to rake the mast rearward to avoid the opposite problem, but same principle applies. I forget if you went with the large sailing rudder and turbo fins. Large waves can overpower even the sailing rudder leading to yaw or even broach.