DISCLAIMER I AM NOT SUGGESTING THAT RULES BE CHANGED OR THAT THE CURRENT RULES DONT WORK
But is there somthing in what Dave says
Obviously with a year cut off for classes its not possible to change to much in the way of elidgibility . If the older classes were remaned eras with a broader scope for models would that encourage more people to bring out their older bikes .
In the early days of VMX 25 yrs ago in Australia ? the current classes ( pre 70 , pre 65 and pre 60 ) were probably well subscribed and the classes made perfect sense following development across that era . Blokes who raced those bikes in the 60s probably came back out for a ride and the class structure suited perfectly .
25 yrs on with few exceptions i dont imagine many of those blokes are still racing .
From a spectator point of view i dont imagine the average spectator would care less if 67,68 model bikes were racing in pre 65 or 71,72 B50s were racing in pre 70 , they would rather see fuller grids and closer racing .
Maybe in time a loosening of the rules and moving to a circa system rather than a fixed year cut off could be a progresive move
To play Devils advocate if someone suggested doing the same to my eras (pre 75 and pre 78 ) i would object ( however that could change in another 10 yrs )