Fish, NICE CAD drawing/solid model!
FYI - I don't know how high you have the motor mounted in your model, but based on my experience, I'm not sure the often quoted formula for setting motor height on a bracket (raise it 1" for each foot of setback) is correct. Distance from bottom of hull to cavitation/AV plate is 3.5" in this picture.
http://i188.photobucket.com/albums/z...plthtclsup.jpg
With motor in this location, the AV plate was UNDERWATER when running on plane. BRP says it should be ABOVE the water! I had Don Herman redrill the motor mount holes as high as possible which allowed me to raise motor another inch. Handling is still fine at this point; can make hard turns at high speed with motor in normal trim position with no blowout or prop ventilation. However the AV plate is still not out of the water, so I think it needs to come up about another inch. For my 30" setback bracket, it therefore looks like the AV plate height from bottom want's to be in the ballpark of 4.5 - 5".
You mentioned a using 20" motor. Most brackets are designed for a 25" motor, to get the power head as far above water as possible. If you go with the V-4 E-Tec as shown, the slightly higher weight of the 25" motor should not be an issue. Denny