there's been a HUGE problem with that here in new mexico (we're under ACA rules, not USCF, which just means there's no cat 5). the 1,2 fields have about 10-15 guys in them, the 3 fields have about 50 and the 4 fields have 30 or so for most races....what they've done is combine 1,2,3 fields to try to force-out some of the faster (read: sandbagging) 3s who should've upgraded but don't. this is the first year they've tried it and we'll see if it works. the real thing that sucks about it is that now the sandbaggers with be the 4s who won't want to upgrade and have to race with the 1s and 2s. -and yeah, all cats are scored separately in the 1,2,3 race, but it's kindof a hollow victory to podium in the 3s while still not finishing with the front group.
anyway, this whole thing would be avoided if people were forced to upgrade. but our one NM rep doesn't have the time/money/desire to keep tabs on every freakin' racers resume.