Speed plates on caravans in France.....

After many years of caravanning in France, I find I am a little concerned over my next trip.... "do I need to put speed limit plates on the back of my caravan?".... I have read a number of discussions, in various places that all seem to contradict each other! I have a Toyota RAV 4 with a gross weight of 2070Kg and a maximum towing capacity of 1500Kg. My caravan is a Sprite with a maximum laden weight of 1240Kg. I "think" this means that the maximum possible gross train weight is 3570Kg and would appear to mean that I have to tow at the lower speed limits, even though my actual train weight will only be 1310Kg, well below the 3500Kg threshold!! Can someone please help with a definitive answer - or somewhere that has one..... Thanks in advance...