Solved

SETUP Vs Practice Time

Assuming these tracks have "middle" values for ideal setup, then that would make the range of variety smaller. What I mean is, if the ideal setup is Soft-1-1 and you use Firm-50-50 then it will obviously be way off and cause something like the 1.2s loss I was seeing. If the ideal setup is Neutral-25-25 and you use Firm-50-50 then there is only about half as much difference, so the change might only be 0.6s.

That's the first thing I can think of to explain why at some tracks the variety might be smaller. However, it still seems an oddly low impact for your team Sam. Let me know how it goes throughout the season, I will be interested to see.

That looks more like it. The numbers seem to be showing what I would expect now.