Hi mate, my Pacific lives in the water 8 months a year in a Solent Marina. I have also replaced the rams last year but noticed the S/S screw which holds the top cover on the stern drive lined up with the worst of the corosion, so now leave it off.
It does hack me off when I see domestic 240v
extension leads running around the marina and dipping into the water. Never mind that someone might electicute themselves thats my annodes fizzing away. I have also doubled the size of the annodes so they now last about 12 months before requiring replacement @50%.
The rate of corrosion as you point out is going to vary, I kinda hope that the five coats of paint on the stern drive will help keep the amount of exposed metals to a minimum. Also the antifouling on the transom and stern drive is different to that of the hull antifouling which contains copper.
We did discuss this a while back and the need to electrically bond everything together, however I am concenered that what every I use to bond the parts together could end up making things much worse.
I also life her out 3 or 4 times during the year just to check things over, and replace the antifouling (normally in May before the worst of the barnacle attacks begin).