I'm sure others can explain in detail, but Tabman (fantastic Bennett representative) recommends putting zincs on the trim planes when in salt water (and perhaps in other specific situations such as certain marinas).
I haven't had my boat in salt water yet, but before I installed the trim planes I drilled a hole to accept one half of a lozenge shaped anode on top of the plane (as recommended by Tabman). I carry them along to install when needed. I'll see if I have a photo.
(He didn't recommend the zincs that go on the angle bracket plane-to-actuator fastener, because then if/when the zinc wears down or falls off the trim plane could become loose.)
Edited to add: Here are a couple of photos (not that you exactly asked how to mount an anode, I realize, but figured you might like to take a gander at them since you very well may add them).
This shows the holes I drilled so that I could add "half lozenge" anodes later - you can see it just forward of the bracket where the actuator attaches. Ignore the big snaggly spring! I was in the process of installing the trim tabs when there was a sudden "bang" and parts went flying.... ran to the transom and found the bottom of the actuator had basically exploded :shock: Some of the parts were pretty far away. Bennett promptly sent me a new one (said it must have been defective as there was nothing I could have done to cause it). The position it ended up in just made it a good photo for showing the hole I drilled for future anode installation.
Here is another type of tab (Lenco?) with a sightly different shaped anode than the ones I have, but similar idea:
This is the type of anode I have to put on the tabs. Just one half of it on the top of the plane (as per Tabman's recommendation). I think it's usually called a rudder anode.
