Eric, I haven't a clue what the gear ratios are in my box, (I'll look it up next time I'm down there), but it is a Paragon, and the only quirk I discovered, is if you leave the filler bolt out while you run her to get air locks out to re-check the level, the reverse no longer works - put said plug - actually quite a long bolt, obvious closing something vital off, and the reverse works again. The ratios seem perfectly matched to the engine, and I only have a left handed, 3 bladed prop, again unsure of diameter, but it seems, again, perfectly matched to the engine. Maybe you can work it out from the recent pic. That zinc anode is about 6" in max dimension.
On the matter of trim, I know is this hull is not very trim sensitive, as although admittedly I have both fuel and water tanks in the lazaret, I also added a new larger hot water cylinder and new heavier batts ahead of the engine, and put a 150litre reserve water tank in under the for'd cabin floor right up near the bow, which is usually full, and trim did not visibly alter. The only time I ever get cavitation is when I really rev her up in reverse - not something usually done. Mind you, if he is really revving to WOT while at the berth, I would not be too surprised with the vessel is restrained there would be cavitation both directions. One wonders how good that exercise would be on the cleats, cap rails, berth and bottom under the berth as well.
I really wish he would come back on and settle this mystery. Someone said they PM'd him, and it was moving the batteries forward. There has to be more to it than that.