I've brought this up before, but it fell on deaf ears. Your extended watts linkage does nothing more than allow taller springs.
The last time I brought that up it was argued that the radius arms are what limit the flex, which is true only due to the fact that rover used a watts link to center the axle. In fact riding behind Justin's P38 I noticed the panhard rear (on the P38) allows more flex than a D2. You'll see a lot of hot rod and muscle car guys using a watts because it is a very easy solution to keeping the rear axle parallel to the body and it is compact.
With radius arms front and rear and adding a watts link you are creating a more stable on road behavior, which allows the traction control and abs to work more effectively...the downside is when you design a live axle truck to handle better on road i.e. more stable, it makes less flexible off road.
The next time you get a chance to put it on a ramp, go up until the driver rear unloads. Have someone take a picture of the watts, you'll see that it is completely bound.
With watts
http://smg.photobucket.com/albums/v...ew¤t=DSC_0656-1.jpg&mediafilter=noflash
Without watts
http://smg.photobucket.com/albums/v.../seventyfive/?action=view¤t=Image-6.jpg
Granted its not the exact same line, but without the watts and radius arms, the tires do not come off the ground, I picked several lines to try to get a tire unloaded but they wouldn't.