I skuff up the inside of the hollow with a Dremel tool and then fill up the hollow side with MarineTex. I then sand the excess off by rubbing the cam on a piece of sandpaper on a flat surface. Then I install the cams in the rudder casting using the "amorphic studs" you can buy at the Hobie dealers. I keep a spare "fresh" set with studs ready to go with my spare parts. If I need to replace a cam during a regetta it only takes a few minutes. Racing in Jersey bays, with sandbars everywhere is really hard on rudder cams! look for the SLIGHTEST deformation in the cam, particulary the hole in the center "boss" and replace it. The previous comment about sanding the blades comes from Fluid Dynamic: Low Reynolds Numbers/Laminar Fluid Flow Theory. The smoother the surface any fluid is flowing over, the less likely it is to become turbulent and delaminate from the surface. this can cause what you are calling cavitation. What I'm trying to say is that if it is smooth enough, the blade will produce so little drag so as to make tacking rudders practically valueless vs the time to tack the rudders and possible system failure of a cam not rotating.

This will sound crazy but carry a (thin)putty knife on the boat. To fix a Jammed" cam simply place the putty knife vertically between the casting and the cam and press down on the plunger with the putty knife. Rotate the cam with your other hand into its proper position.
Good Luck