First of all, welcome aboard! And, no this forum is not just about Bristol 29's, although we can get pretty specific about them--it is about any older classic built of fiberglass and certainly about any model Bristol Yacht. So your questions about your B27 are certainly welcome.
The differences in the B27 and B29 are mostly these: the B27 was a Carl Alberg design--historically it was the first boat built by the Bristol Yacht Company. The most famous Alberg design is probably the Pearson Triton (at 28 feet). The B29 was the second design that they undertook. The B29 was designed by Halsey Herreshoff. The designs are similar in many respects: Alberg's has a bit more sheer, more to my liking, but the boats look very similar and were built side by side at the same time. The B27 has a foot less beam, 1000 pounds less ballast and about a ton less displacement. Her waterline length is about 3 feet shorter, but both boats are great sailors--Halsey specifically designed the B29 to be fast in racing as well as cruising while Alberg was looking more at just cruising I think.
I don't want to drift the thread too much. I'd be happy to expand on the first generation Bristol designs and everyone is welcome to add their knowledge. I think we would all love to see photos. If you have trouble added them here, let me know.