Got to do some testing with Brandon Shells this week with the new 1S lipo. In 17.5/NiMh configurations both of our cars are virtually equal in laptimes and both of us have reset each other's track records through out the spring and summer at the local tracks.
With my car configured with the 1c lipo it's right at .15 sec per lap slower across the 8 min run. I'm going to work on a few setup changes and see if I can't craw that disadvantage back. Currently at a ~92mm rollout with 17.5.
I'm not sure but I think a fair comparison to to 17.5 nimh hookup is 1s lipo 13.5.