Hi, just read through from the start and its looking good!
I am 99% certain that your shell is a Banks 47 shell, there are a number of reasons why i say this (colour of the shell when you got it, inner rear arches being 'twin cam' style, A pillars etc etc...) - i can see various openings/holes that haven't been cut out and it would have been supplied solid underneath where the tanks fit so that the builder can choose how to fit/mount them etc... Personally i'd use the extra depth of the wells to mount the tanks lower and give yourself a little more capacity - i can remove my tank from the top by removing the Roll cage rear stay that runs over the top (mine might be easier to remove than yours though?) - i did make a cardboard pattern, like you have, and had the tank made to suit with this in mind (just incase i was ever at a track and it needed to come out - the car has to lift a long way up before there's enough room to remove the tank from underneath!!)
Your pedal box looks like a 47 copy, Banks did supply those but it doesn't look like one Richard has made. Generally Richard sold his own pedal box that has a removable lid and four sides (His own design met with modern Blue Book rules that prevents fluids etc being able to make it into the cockpit) - There is a pic of one on my car thread with the lid removed.
A Naca duct mounted towards the rear of the front bonnet works very effectively at feeding fresh air into the front plenum/interior ducting. My rad is ducted out through the bonnet like yours and the Naca duct catches some of the warmed air that has passed through the rad and i can use it to prevent my windscreen from misting up whilst also circulating fresh air (no heater in mine).
Sounds like you've escaped Windsor just in time!!