I sat pillion on track last year with ex BSB rider Matt Llewelyn. I felt safe as houses and we were right over, and the braking was immense!!
My arse was off the seat, and both feet off the pegs, I was just like his rucksack, bracing my weight with my hands on the tank, around his waist.
His big back end slide to finish was fun too, 30ft of tyre scrub, when I looked at the back tyre it was flat spotted and smokin with a contact patch about credit card size.
A brilliant experience :)