I installed Corian counter tops in my 1976 31' Sovereign
about 5 year ago. I used the 1/2" material. When you take into account the cut out for the sink and stove top yop are not looking at a lot weight. I also installed a under mount sink which sits on a 3/4" plywood base and the Corian is attached with silicone to this. I have not had any problems after a lot of miles down the highway.
Here are some pictures that includes before and after shots as well as some of the construction shots.
Good luck with your project.
1976 31' Sovereign