I'm 160lbs on a 17lb bike.

I ran 35f/38r psi on my 34mm clinchers last year for racing. I bottomed out lots on roots and curbs, but never pinch flatted - although I'd imagine it would have been a matter of time.

I'm on tubs this year, planning on 28-32psi for those.

I run 50psi if i ride on the road on those tires. Nice compromise between comfort and rolling resistance.