whats the correct position to be in when setting sag on a full susser ? i.e seated , standing or somewhere between the two. opions gratefully received.

most say seated

It all depends what you want from the ride and remember that it's only a starting point.

Two things to remember are that it should match the front end. Also, if you're riding at your limits, you want to be using all the travel (without harsh bottom out).

I've always used 25% in the seated position after bouncing about for xc/trail

and 1/3 sag sat upright when I'm playing on bigger stuff. But remember, tweak from there. The biggest mistake lots of people make is not tinkering enough with the settings.

I run 1/3 sag front and rear.

Rear is measured with ride gear and full camelbak, seated upright on the saddle, with arms off the bars.

Front is measured with the same gear, leaning over the bars.

YMMV