Mikey,
The matrix signs only indicate a maximum speed. They do not necessarily indicate a safe speed. A safe speed may be much less than the matrix shows.
David,
Your question is rather like "how long is a piece of rope" I hope it is fairly obvious that the greater the wind speed, the greater the thrust it will exert on the caravan. the direction of the wind is important, as well as how sustained the speed is.
If the wind speed increases, the thrust also increases and eventually it will cause any caravan to become unstable.
Other than zero, there is no single winds speed at which you can say that it wont affect a caravan. and different outfits will be affected to a greater or lesser extent.
As always it is down to the driver to assess the situation, and to make a decision about driving in the prevailing conditions. If you feel unhappy about driving, the you should not.
You should always obey the matrix signs, but as with any speed sign they represent the upper limit, and you are perfectly at liberty to drive slower if it is safer.
eventually any caravan will be adversely affected, adnd may