The Pearson 28 list on Yahoo Groups is moderately active. There isn't much discussion on the Pearson 27 there, but you could try:
I don't think that many Pearson 27s were made. There were only about 200 Pearson 28-2s made, and the Pearson 27 comes up for sale about 1/3rd as often from what I've seen. It looks like a cool boat on paper, but I've never seen one in person. The Pearson 28-2 has a larger interior with two double berths for not much more money, which is why I think it is more common (both were sold at the same time).