Based on my limited experience some things to consider in laying out and fabbing a lakester drivers compartment.
Design it big, far easier to shim supports and padding in to fit future smaller drivers or owners than have to rebuild larger later. Factor in provisions for adjusting seat, control, and pedal positions for the same reason.
Take all layout measurements with full driver gear on or close mock up substitutes such as heavy insulated winter coat/bib overalls for firesuit, strings/straps for arm restraints, helmet same as or very close to one to be used, head and neck restraint device, etc. Factor in the recommended belt/harness mounts and routing for the system you choose. Usually having all adjusters pulling towards the central latch works best for lakesters. Little differences in eye port in helmet / seat layback match for line of sight can cause issues later. I wear bi focal's and discovered that a pair with just the distance portion ground in worked best for me to focus down course with the tach needle position in view at the same time. Glanced at the water temp and oil pressure needle positions at the start line then after going through the lights, saved any close number studies until reading the data logs later in the pits.
Tip from another lakester team that really helped us - some switches are more easily operated with arm restraints hooked up when mounted across the body on the opposite side. We located the inertia/roll over electrical cut out (used a stock Ford) for the electric fuel pump there for a quick reset if necessary alongside the elec water pump switch and starter button. Another tip from same team that works well - vertical post just ahead of the quick disconnect steering wheel for wheel storage and use as a handle for driver to pull forward, up, and out of the cage during exit or bailout.
Used a pull to activate fire bottle cable after seeing a push to activate cable on another lakester get broken right at the pin hole when a crew member happened to hit it while reaching into the cockpit to do work in the pits.
Car I drove is all set up so left hand can remain on the wheel at all times with the right operating the shifter and all other switches and controls. Just seems the most natural to me, I figure more natural comfort equals more time and focus for the driving. All done while keeping an easy smooth bailout with the least amount of time required in mind.
Stay safe, have fun, go fast
Ed