I once saw a wonderful and very strange seki, which now seems like a dream, as I can't remember it precisely, and it has disappeared from the internet! I'm very surprised that the seki page on SL doesn't show it as it is quite different to all other sekis.
It looked something like this, in that there was a large single 3 x 2 eye for black against the edge, but this is not it:
The last diagram in the Cutting Seki page is probably what you're looking for...
Absolutely fantastic Mr Tenuki! I was starting to doubt my own sanity. Thank you very much.