Harry
Thanks for the thread it's always nice to hear good things about Cat Sailing.
If a F16 Class Flag isn't available could I suggest adopting the Y-Yankee flag.
The Y Flag is made up of yellow and red stripes which is similar to the Spanish Flag. A Spanish explorer was the first European to discover The Chesapeake Bay in 1525. Also, The Chesapeake Bay was the venue for a Naval Battle where the French defeated the British Navy during the American Revolution in 1781. British Officers nick named American soldiers Yankee doodle dandy's due to their extravagant uniforms.
I hope you get where I'm coming from. Anyway, it was just a suggestion!! and I hope you have a great regatta.
Not a good idea, since the Y flag has a defined use under the RRS (Wear personal flotation).
40 PERSONAL FLOTATION DEVICES
When flag Y is displayed with one sound before or with the warning signal, competitors shall wear personal flotation devices, except briefly while changing or adjusting clothing or personal equipment. Wet suits and dry suits are not personal flotation devices.
To avoid confusing competitors and lacking a specific F16 flag, use a unique color flag (pink, brown, green, etc.) or one of the number pennants. Code flag zero has red / yellow vertical stripes.