[Aussie Mike]

I think the problem with Jag rear discs on a Cobra is more that the air cant get to them. On a Jag sedan the floor area in front of the diff and brakes is much more open to air flow. On a Cobra the tub where you sit comes right down in front of the brakes and shields them from much of the airflow under the car. Rather than fitting ventilated discs I'd be looking at trying to duct more air in to the standard solid discs. It shouldn't be too hard to make some ducts down in the air flow and get cool air in to them.

Another option would be to adapt up some Commodore finned aluminium rear calipers and hang them off the back of the diff. The finned callipers should dissapate the heat a bit better and having them mounted on the back will give them a bit more air. Combined with some air ducted to the discs I reckon it would work well. The rear mounted calipers would be much easier to service too.

The only problem I know of with the rear mounted calliper arrangement is what Les mentioned to me. Suposedly there can be a problem with hot brake dust being thrown up towards the underside of the car rather than down towards the road. You may need to consider an aluminium shield to stop the fiberglass floor being dammaged.

Cheers