I guess there are three issues here:-
Can You ride down an age group? As per the rules, a rider cannot elect to ride in a younger group, however it seems when the younger age group has insufficient enties to qualify as a championship, the oganiser can combine two or more age groups to make up the numbers. For example, at Griffith I entered Pre75 125 Over 60 but ended up being cannon fodder in an "Over 40 125 class" No chance against riders 30 yrs younger,but it's a ride and makes up the numbers.
In the instance where you have say 10 riders in 40-49 & 10 in 50-59, with a 40 rider gate, the answer is run them together [both qualify as a championship] pointed separately.
There is an issue with the new 60-69, and 70+ classes. Over the past two MX & three DT Nats there have been Supersenior awards.Not a separate race, but a recognition of the "over 70s" continued participation.They rode in the Over 60 classes plus whatever else their bikes qualified for. For 2011 MA decided to recognise the over 70s in the rulebook.The thought is greatly appreciated, but it has backfired in that it is now 60-69 and a separate 70+.I know the proposer didnt intend this ,so it is an admin error. The ramification is that there are insufficient riders over 70 at any one meeting to justify a race [and a separate race was never the intention], yet we are ineligable for 60-69. Our only option therefore is in open classes. For the DT Nats we have the 60+ classes plus 70+ awards. Hopefully this will apply at Chrystal Brook.