I use Panaracer Tour Guard 175s on my Raven, rated at 65psi. This is fine for daily use but when loaded up with camping kit and 3 yr old child I think they could do with more. I know some people, particularly tandemists exceed the ratings and there are even arguments that it's actually safer to overinflate but by how much? Can anyone recommend what I can safely use? 80? 90?[?]