John Rumm wrote:

Perhaps it depends a bit on if you are using 9 or 12mm board, I usually
use 12mm and have never noticed any sag at all in the space of 400mm
(i.e 32 screws per 8x4' board).

First time I put PB up I just put one screw in the middle of the sheet,
and said to the guy I was with 'thats alright, innit.' The look on his
face was so funny


NT