Martin, what I meant was to group the models in the way they will be sailed. Warships, Service Craft, Tugs, Lifeboats, Trawlers will all be free sailing models. You need to know what provision to make for the "organised" parts of the event for which you will need to reserve all or part of the lake. For example, (you have already mentioned some):
Springer & Springer Football,
Straight Running,
Club 500 racing heats,
Other electric speed
Warships display.
Tug competition and display, (Towing?)
Footy and Yacht races,
IC boat demo/race (Inc OMRA boats) - probably needs to be Saturday PM from what people have posted
Footy Yacht Race
Steering competition?
Twilight sail past with lights on Saturday evening
All this lot will take up quite a bit of time and space and some, such as the IC boats will need exclusive use of the lake. Whatever time is left over can be devoted to free sailing with a managed frequency board.
You do need a realistic schedule otherwise some people could turn up and find that they can't find a slot to run their boat(s). It may be Mayhem, but you can't afford a free for all like the scrum at a Ryanair Boarding Gate!
Colin