I've not driven the car for ages due to work, but the SC setup was working well last time I did (especially considering it's still a work in progress), the only issue is it's not too happy in heavy rain - an issue I must try to get to the bottom of this year. There's still lots to do (bigger oil cooler going in badge panel, seal off underside of engine bay, have a side exit exhaust made, add diffuser, proper remap and then the new engine sometime next year hopefully as the rings are well past it on the current one).
Those rear seat belt brackets are going, but I'm not sure if the mounting point for the rear seats are too - I don't think Alan is planning to paint that far forward this time.
The battery I'm using is a small powervamp model, I'm not worried about the weight distribution at the moment, if I believed everything I heard my car should handle like a dog with a 35kg supercharger right in the nose, but it doesn't. I'll get it on a proper set of scales when I'm 'finished' and see what the weight distribution has ended up at, I'm not expecting the car to be that light as there are quite a few heavy additions (brakes, wheels, SC etc) and we didn't dip the bodyshell before starting (probably my only small regret).