The ratings: The method for Portsmouth ratings usually start high then work their way down as more data/more boats roll in. I don't think we've seen the "real" number yet. It will be more like the F18 when it is all said and done. I feel comfortable racing the F18s boat for boat (obviously they will fare better in certain conditions and the F16s will favor other conditions).
My thoughts with distance racing and using Portsmouth are less than enthusiastic, especially distance racing with "straight line" courses (point A to point B in one general direction). The finishes are dependent on boat characteristics (paired with that particular day's weather) rather than all around performance. I don't even think US Sailing counts distance race times in their calculations for indexes.
I read some about the GTR and it sounded like a handful. Congratulations on a great race. Some very beautiful scenery along the way. There is an interesting post on the Distance Forum about proclamations made by certain vendors after the finishes were tallied.