Dashaw,
I have been trying to find an example of a O27 chainplate in pictures of sales ads, online parts catalogues or online salvage yard inventories, but no luck.
The interior pictures to either side of the forward suite bulkhead all have a headliner covering the underside of the deck. While the are lots of 27s for sale, there's not much for parts online.
It seems like there has got to be several members here who own or have owned O27s and should be able to scrounge up a picture or two. Be patient, someone will be able to help. This is an awesome group.
In the mean time, I can help keep your post fresh.
The 27 looks like a nice boat. Good luck.
-Will (Dragonfly)