I feel that this is integral to a level playing field, although I'll suggest the minor wording change in bold, and I would add something along the lines of -
If a tester without PSN access is unable to acquire all cars needed by the final deadline, any times submitted will be removed from the final results.
While I'm talking about PSN access, what about a standard caveat of -
In the event of a major disruption to the PSN, outstanding deadlines of any current shootout will be extended by the amount of time the PSN is unavailable.
Worst case nit-picking I know, but risk assessment is a major part of my job, and I find it hard to switch off sometimes.