To allow the relative motions only along the spar local z-direction, please defined the pairs of fenders, which are fixed on torus-shaped WEC and the contacting surfaces are defined on spar, on two horizontal planes, as shown below
The fenders you defined which the fenders' axis is in relative vertical axis are still valid for modelling the PTO system. I wonder the sizes to these fenders could be bigger?
You are navigating away from the AIS Discovery experience