I'm currently in a club for which mixed fleet racing is the only option. One problem we face is arguments over the assigned US Sailing D-PNs.
We have a very wide range of boats - J-22s to Sunfish. The fleet covers several discussible numbers such as: American 14-6s (96.3), Holder 14s (93.2), O'Day Mariner 19 (104), Hunter 212 (93.2), and new model Hunter 22 for which we've been using the H216 number (90.8). (The H22 is listed by US Sailing at 96.5, compared to the 212 at 93.2!)
I've been following Portsmouth handicapping for a long time., and I'm aware of the problems of really "fair" comparisons over a range of boat types, design objectives, wind conditions, etc. However, I'm wondering how other clubs have dealt with the issue.