Hi Tony & Peter,
The reason the Mosquito is grandfathered as an F16 boat is due to the fact that the South African (the other "SA" ) Mosquito Class had a vote to adopt the spinnaker as part of the sailplan, and came up with 100% of the members voting for it`s inclusion. Prior to that there were only 5 or 6 of us sailing with a spinnaker, and as we were sailing outside of the Mosquito class rules, we felt it would be beneficial for us to belong to the F16 class, which in turn benefitted them since it gave them a presence in South Africa, something which in time should start to grow (slower than other world markets unfortunatley). I really look forward to seeing other makes of cat join into F16 here, but for now we only have Mosquito`s as F16, and we are grandfathered (or dispensated) for being under the min. weight, in exchange for having a much smaller rig than is allowed under the maximum specs.
Since the vote on the spinnaker was positive, our class has gone to 24 odd spinnaker boats, unfortunately that is 99% of our fleet, would love to see more mozzies but no-one is doing any marketing, a general problem in sailing.
You guys have a different situation - the class rules haven`t been amended to allow the spinnaker or include it, and so you can`t use it when sailing in-class ie at Nationals or State titles etc. What you do find though is that at open events the Mozzie guys who have added kites now have the desire to race open events and will attend more of them, since they are no longer regarded as slow boats and have a shot at doing well, and are sometimes "waking up" the bigger or traditionally faster boats. Taipan and A-class sailors don`t enjoy watching Mozzies pass them downwind, I`ve heard . I have personally annoyed a few Hobie Tiger sailors downwind.
My advice : Just get yourself a kite when you`re ready for it, you will add one more to the numbers who can vote for it`s inclusion in the class, and one day the class rules will catch up with what the majority of the sailors want.

Cheers
Steve