You outline a lot of variables in your race. First off, your description of the two boats' displacement and ballast weights makes it seem that the Tanzer might be the stiffer of the two boats. with 1900 pounds in her keel vs 1700 in the Niagara. In a nice breeze like you had, this could make a difference. You mention crew placement. Your two in the cockpit may have been making your stern drag and cut down on your surfing. Overall crew weight on two boats could also have been a factor. Most, if not all of this race sounds like it was downwind. You should be aware that PHRF ratings are supposed to be based on boats racing a triangular (windward, reach, reach) course. If the race course doesn't include sufficient upwind work, the rating is going to be "off" for that race, just as it would be "off" if the race was only upwind. Some PHRF fleets allow rating adjustments for such situations. Perhaps your boat outperforms the Tanzer upwind, but not downwind. In this downwind race, the larger masthead spinnaker of the Tanzer may have helped them pull out despite their overall heavier displacement. Having the outhaul only half out in 20 knots of wind seems a bit too loose IMHO, but it's hard to say without actually being there to see it. As others have suggested, a spinnaker almost 30 years old is likely not speedy either. If you can't spring for a new one, go for races that use it less and let us know what happens.