Donkey!, have you explained why you went with the space saver wheels? I did a search and just came up with
http://ecomodder.com/forum/showthrea...els-16886.html and
http://ecomodder.com/forum/showthrea...uts-19094.html. I wondered if at least part of the reason that they are only rated at 50 MPH and 50 miles is not because of any lack of the donuts themselves, but because they do not match the other four tires, but if you have four donuts, especially in your case, where you have real tires on them, if it balances out.
I know that we avoid using our brakes, but how is your stopping distance?