John, about 1200 lbs of SAR role kit and 4 crew @ 200lbs each makes up the 2000lb difference. We use ZFW instead of APS as it includes the crew. Our 6371lb (when gravity refuelled) 6239lbs pressure has always been the same - don't know about the Danish and German SAR SKs, every Mk seems to have a different fuel tank layout and capacity.
There are a number of jungly SKs with Carson blades fitted under a SUR for sandy places and many of us are hoping we can have the whole SK fleet fitted. It deosn't give us more absolute Vmax but makes the same Vmax available throughout most of the flight envelope.