I have a soft spot for Berlinettas so keep the progress photos coming.
A couple of thoughts on the seat belt issue.
The Berlinetta was never designed to meet the current safety requirements of kit cars: it is too narrow to be able to raise the turret height for the seatbelt mount, as the tops will then stick out of the side of the hood/hard top.
One option would be to fit a 4 point harness secured behind the seat, as in "racing bucket seats" - the seat must be strong enough to take the loads imparted on it in the event of an accident. I guess the praticality of this depends on whether you want to make use of the Berlinettas "rear seats"?
Another option to help is to make seat recesses in the floor. Marlin used to offer these at 25mm deep for the taller driver.
I welded recesses in my Cabrio with 65mm drop depth at the rear (25mm at the front) - this would solve half your problem, and make it easier to find the the remainng height from an additional modification?
