You should be ok on the stress front as you will be same spec as the SLR racers as far as I know. In that vein you could go for the same size wheels and tyres as are run on the race cars. Taken from the Caterham web site...
Front: 6.5" x 13", Avon slick 7-20-13.
Rear: 8.5" x 13", Avon slick 9-20-13.
Graham