Thanks for your replies, i took a while for me to answer, we were on the road back to home and WiFi was not available everywhere.
i took some measurements, the trailer is a bit wobbly when the legs are extended about 45cm, which happened more than once during the trip to Tuscany since camping grounds tend to be sloped over there.
So to get the trailer leveld it was sometimes needed to extend the legs about 45-50 cm and using some wood of about 2.5cm.
Most people seem to use bigger blocks so i will be on the look out for some big blocks of 8-10 inch or create something that big.
We arrived home today and on level ground the trailer only needs about 25-30 cm of leg hight, tested it, it is very stable now.
So agaIn, thanks for your replies and helping us figuring out the best way to do things.
Severinus and Yvonne