If the wheelbase remains stock, then the image above shows what is likely the minimum reasonable size for my body size - 6'2". I am gradually homing in on the sizing and ergonomic compromises.
Slightly larger would give more elbow room of course.
A longer tail and more careful curves would pay dividends.
Even a boxy version will achieve the short term goal of affordable weather protection without breaking the bank.
My experiences with the more open fairing seen in previous videos convinces me that the vehicle's fuel efficiency has already improved a surprising amount. The much more closed version pictured in this post should further increase fuel efficiency.
No hard numbers yet. Still playing with fuel tank issues.