I agree with Andy (ASdesigns) - as for me, the track itself limits what I can run.
I've turned up and ran a 5.5T with no timing, a 6.5T with timing, and now a 6.5T with no timing and geared down.
This is the best setup for me and the tight track I believe.
So if you want to set a limit, 6.5T with no timing is fine for me, but Im also happy to leave it open.
Cheers Ed.