I'll admit, I've been sceptical about relying on overclocking for something that is actually being used but I suppose if it works at 96MHz(!) then dialing it back to 80MHz does provide some margin.
Since it's going to end up in a car I'd probably test it at something other than room temperature before banking on the extra instruction cycles. I know you said it did work in the car at 96MHz but at what temperature?

Looking forward to the optimisation thread!