same situation in italy, race weekends do have some 300 racers registered, but when you split them into all classes (including regularity) you end up with some classes having up to 15 people max, many others dwindled to 6.... What to do then? Tell people it's not a worthy championship, so stay at home please? Our federation tried to bunch up all pre 79' four strokes into one class, but was is the point of racing a 500/4 against a Z1? Luckily they retired the idea even if it's only 6 riders in 500 now but who still love their bikes and want to race.
From what I see in other vintage championship rounds in Europe, like alpe-adria or the german vintage guys that came this year to italy for a round, it's the same situation, numbers constantly declining, only the newer classes like early nineties SBK and SSP600 having reasonable numbers. Not exactly vintage though...
I think that it's only the UK that stands out in having such big grids for each class, not to mention so many guys running G50/Manxes like in Lansdowne series.