Thanks Bicycle Bob and Joe for your messages.
This is the side profile of my body so far. The top of the bodywork increases in height until about halfway which is where the cockpit opening starts and I don't have much control after that due to all of the turbulence in the cockpit.
The channel underneath as seen in the picture, starts quite late, just in front of the front wheels and has a smooth transition from the nose to the fairing. The ground clearance at this point is the maximum I can have it at and it does increase in height at the rear, producing a slightly low pressure area underneath, which is at a lower pressure than the airflow on outside. I think this helps to reduce the amount of airflow bleeding from the channel to outside the body and keeps the airflow at the rear relatively neat. Hopes this makes sense.
The cockpit opening and the roll bar is fixed, can't do much about them.
One of the disadvantages of using tiny 305ERT wheels is that they have almost no deflection in the wheel and the smaller circumference makes it have higher rolling resistance. I have thought about using minimal suspension, but the amount of space I have inside the car means that chassis flex done correctly would be better solution.
Joe of Loath - I always have wondered what's it like to drive one of those, I raced closely against one with same design but in carbon fibre at the final of 2013 and it looked good, is it slightly more unstable in the corners or does it not matter too much? Also did you ever use or experiment with derailleur gearing?