Is there a handicap system that allows old and new boats to race together?

I believe there is a graduated PY handicap system depending on the age of your boat for club racing. If IY google death Merlin rocket PY for handicap racing you’ll find it. 

Nothing that I know of for fleet racing. 

Its here on this web site, have a look in the PY section which can be found in the "About" tab, if your an association member (full or associate) you can find the info in your year book too.