There are several reasons why I think you're not getting anyone to jump in here and give you a definite answer:
1. The topic has been discussed before, at great length. Just about all the wisdom available is there already.
2. You've read all those posts without coming to a conclusion-this shows how difficult it is.
3. The exact solution/answer/pitch depends on your type of boating, boating venues, loading, engine rpm preferences (within the range recommended), prop metal or other material type, etc.
4. You're begging the question for an exact answer, which apparently no one wants to go out on a limb and GUESS.
My best recommendation for such a situation would be to go to a dealer which could provide you with a number of pitch alternatives and try them out one at a time. If you pay up front, they will then let you try various ones until you get it right to your satisfaction. This is harder to do in a 4 blade design because there are less available choices, but what you're obviously trying to do is avoid buying the wrong one and getting stuck with it. Also there are specialty outfits like Prop Tech that design their own products and can split hairs between pitches, rakes, cups, blade design , etc.
Have you seen the September 2004 edition of Trailer Boats Magazine? It has a review of five of the 90 hp outboards available, including noise ratings. The article left out the new 2005 Yamaha 90 EFI--too recent to be included. I have this last motor and I am very impressed with it! That same edition also discusses prop selection rather thoroughly, at least to those who haven't studied it to death already.
You could alternately try a Pro-Pulse adjustable pitch prop or a ComProp which are both 4 bladed props to find the correct pitch-but I doubt seriously that the pitch in one of those would directly convert over to a stainless prop, depending on the design of the latter.
I'd start with 16 inch pitch and go from there!
Maybe now other will chime in and give us some other ideas? Joe.