Now that my 15yr old is sailing my old F16, I've considered arranging a reef in the main. I've thought about copying the system that RS use on their Vision family racer. This is a horizontal heavy duty zip that has each half sewn about a metre apart on the sail. Pull the sail down so that you can zip up the two halves of the zip and bungee on clips on the other side of the sail tidies up the bunt of the sail. Retension the luff and you're set!

The variation I was considering was to arrange the zip to take out a full lower panel between two batten pockets. I'd also have to fit another halyard lock hook at the correct height on the mast to take the head in its new position. I suspect also that with the amount of luff tension we use compared to dinghies that I'd also need a new cunningham point just above the zip and a mainsheet take-off to match at the leech.

As I say, thought about it but haven't done anything about it just yet.