Bought a used WPP Plus from an over 40'/25,000# boat and installed it on my Pearson
35. Sailed the boat downhill to Hawaii
without a hitch. Winds were light for that passage
usually around 8-10mph relative and course DDW which is typically the hardest point of sail and conditions for a self steering
vane to handle. The WPPP rudder is quite large but didn't seem to hurt speed as I made the trip in 15 1/2 days averaging over 140mpd. Sailed wing and wing with the 135% genoa
poled out for 13 days of the sail. Only modifications to the vane was a 8"x4' lightweight plastic wind vane
to increase light air sensitivity.
The length of the vane was a minor issue. Mounted it as high as possible on the transom but steering
rudder shaft coupling was right at the water
line. Peter recommends 8" or so of the rudder out of the water
at rest. Didn't effect steering
ability so not a big thing but I didn't thoroughly coat the stainless fasteners on the connecting coupler between the rudder and the vane stock with lanolin and had a hell of a time getting them out. Shortened the vane casting and rudder stock by 8" so rudder coupling is now high enough it doesn't constantly get dipped in sea water at anchor
or in the marina and bolts corroding are such an issue.
So, yes the vane is probably more than you need for your boat. The smaller version will be lighter and should fit without a hitch. The used one should be way less money
and will probably work just fine if your boat does not have particularly low free board at the stern.