I have created an assembly and inserted 4 DeStaco clamps.  I want to place the clamps in a precise location but am unable to create associative dimensions.  I pick the edge of the fixture plate and the center of the clamp shaft and I get a dimension, but I can not change it.  I have attached a zip file of the assembly created so far.  Still work to be done like riser pads under the clamps and hole locations for the clamps.  Any and all help is much appreciated.

Thanks,

Mike