My GTN was set up by Richard Thorne at 24psi (~1.7bar). Still running on Yokohamas.
Had it on your wonderful Belgian roads last year - could certainly feel the thumps/bumps but no impact on handling except for the odd, brief lift-off. My sensitively calibrated meter (wife) actually commented on how comfortable it was!
I do find the handling very sensitive to unbalanced pressures (e.g. 1 tyre out +/-) even by small amounts.
