Only way that I can minimise the impact of the roll bar is to reduce the size of it. I can't have any fairing or aerodynamic aids on the top 150mm of the roll bar and this would include the helmet fairing. Therefore I only have 150mm of roll bar exposed above the fairing as I did on my last car. There has been trend in the last few years to make the roll bar smaller and hide them behind the helmet.
The racing is done normally on airports and racing circuits and therefore for a small car, the track is large, smooth and doesn't have many tight corners. Almost no teams run suspension, probably because it's not really necessary and can add weight and complexity to the car. Here is a video of me driving a previous car in 2013 final to show what a normal track and race would be. Also shows that only minimal steering range is needed.
Nothing is allowed above the driver's eye level, even windscreens aren't allowed above that level due to this rule.
T7.4. Bodywork, including windscreens, to the front or sides of the driver’s helmet may not be higher than the eye level of every driver. This does not include front wheels or their coverings.
The 305ERT wheels would have less deflection up and down than 16" or 20" wheels and especially with my wheel which has a 28 or 32 spoke count, which is high for a such a small wheel.
Yeah, although the horn design did give a quite low drag value, my modified catamaran design had even lower drag, mostly due to its gradual increase in the ground clearance and is mostly likely my body of choice.