Regarding tyres on a Porsche engine van, I recently read an article that
took your typical NA family slush bucket, and went from 14" garden variety 
tires to 16" low profile performance tires of the same diameter, slightly wider.
Even the authors of this performance oriented mag were totally stunned
at the dramatic improvement in performance,and handling. They were totally
blown away with the difference. Sorry, but I forget the name of the mag.

Bill Crick
76 Type II/IV/VII

PS: Do Type II's slide, or roll first? IF roll, which tire lifts first? How do 
    you tell? How soon before the second tire lifts, and how do you tell?;-)