A change in the IC of the rear suspension will cure the squatting. Search the net for tuning. There is an Anti-Squat line that runs from the contact patch of rear tires to horizontal center of gravity line at the front axle point on your car. The lift point of the 4 link bars in relation to that line, above/below, will cause different reactions in body/chassis. Bob has good suggestions.
http://www.how-to-build-hotrods.com/tuning-4-link.html
When the front hits your UCA bump stop, it kills weight transfer. Maybe trim 1/2" off the upper stop.
Keep at it! :cheers: