with regard to the panniers, my advice would be to always use them in preference to a top box or tail pack.
The panniers are above the rear wheel spindle, whereas a top box is way out behind this, much higher up, and really can make the bike move around at 3 figure speeds in windy conditions (no more than any other bike with a top box though). The panniers on the other hand have very little effect that I can detect.
I can say from experience that they don't fall off even when doing an indicated 150 and above
As for tyre pressures, I always run those given in the manual, which is 38/42. My experience is the handling deteriorates on lower pressures. Obviously different makes of tyre respond in a different way to this.
I posted something recently to ask others what pressures they run, and it seems most run less than this, but just 2psi down on the rear is enough for me to notice it in faster sweeping bends.
by the way, if you cant get the eyelets out the link rod without damaging it don't get too upset, a new one is only about 16 quid.
Cheers,
john.