Jeff, here's another idea for shape of the cabin top, the
Moesly 27 Seamaster from Carla's web site, sort of a Seafari on steroids! BTW, you'll enjoy that web site - Moesly is also a pilot, and with over 13,000 hours, he's flown most of the WWII vintage aircraft!
Here's some shots of a 27 near me that was for sale a year or so ago.
Denny