Swing keeler slot gaskets

[Jakest]

What is the widest centerboard, or in my case swinging keel slot that can be bridged with a dinghy type flexible slot gasket? I wish to fit a slot gasket to my Swift 18. If necessary I will make a single piece one out of stainless plate that slides up tracks from aft, but I would have to remember to slide it back when lifting the keel and there would obviously be less to go wrong with a flexible, split down the middle dinghy type approach, but the 10cm gap or so I would have to bridge might just make it too wide a gap. The flaps will have to be pretty stiff for the waterflow not to just deform them behind the keel and continue to circulate in the keel box. But would such stiff flaps be too stiff to deform to allow the keel to go up and down? At its thickest a Swift 18 keel is about 75mm thick.
Anyone got any ideas? Anyone know of any swing keel yacht (as opposed to a centreboarder) that employs a slot gasket?

 

[Seajet]

I have a lift keel boat but have never heard of people using a slot gasket; I am familiar with racing dinghies so I see what you're getting at.

The first snag which occurs to me is, how are you going to fix it to the hull ? I can't imagine even the best adhesives putting up with it, and I for one certainly wouldn't fancy loads of screws and holes in the hull.