Mike,
I don't think the Seafari 20 has nearly as much weight up forward as the 23WA. The bunks should be about the same weight as the fwd casting deck and fishbox on the CC models, and the cabin top is relatively thin glass (about 1/8") with no core in it. The Seafari 20 cap we got for Skip & Carla's 21 is easily picked up by 2 guys; I'd guess it weighs maybe 50 lbs with no windshield on it. I've never heard of any ballast weights being used in the Seafari 20 like folks have found on the 23 Sceptre/Tsunami's. I believe the later Sceptre's (and probably the WA's) also used plywood cores in the decks instead of the balsa core used by Potter, which would add some weight up front.
This shot
shows my AV plate was 3.5" above the keel BEFORE we raised motor another inch. What works on the 20 might not necessarily work on the 23, but there are 4 holes in the mounting bracket on motor, so you might want to consider starting out with the 3.5" AV plate height with mount bolts in 2nd hole from top. That way you could raise it 2" or drop it down 1" to fine tune it. Or, just install a jack plate, which will move the motor even further aft, but that shouldn't be a problem with your CG location. I considered a jack plate, but my motor is already too heavy for the boat with the 30" setback, so I didn't want to shift the CG even further aft! Denny