The floor is almost done. It's basically an aluminium tray that mounts to the sill and to the body brace the runs fore and aft. We've left a gap in the middle for gearbox/diff cooling as plumbing in a pump and external radiator is a bigger job then we've got time to undertake.
The exhaust exits through the boot lid!
We've kept the lights in as the long term plan is to do longer endurance races that go into the night. The cold air feed comes from the radiator intake in the front bumper. If you look closely in the first picture above you can see it in the bottom right hand corner.
We've only got a fibreglass bonnet at the moment, but more parts are in the plan. I don't have the knowledge to make moulds, but do know a few people who can, so possibly will look into it next winter. As you say, a standard hard top will not fit, and is very heavy, but it needs something as it is a much more aero-efficient car with a roof.