My turtleback 1.5" higher than plans, and it is also installed higher than plans. Specifically, at the front end it's lifted another inch above the longerons, and it's spread at bit at the front edge so it doesn't produce as much of an internal overhang above rear passengers' shoulders. This area is normally hidden under a fairing anyway, and it makes the interior feel a bit more spacious for tall passengers.

Some fill-in was required with foam and plywood, but otherwise the installation was per plans.