Sorry Sunflower - didn't mean to be nasty.
It's just that I work with lots of techies in IT, and time and time again the last thing they resort to after days of trying to rebuild a system from scratch is to read the manual. Then they find something obvious they should've done in step 2...
Ah well.
For most of the cars I've owned, the manual suggests adding around 2 psi if you're travelling fully laden. I tend to keep it around that level anyway (when I actually bother checking!
)