John,
As I discussed in an earlier post, might have been on Skip's thread regarding front suspension, if you run wish bones, split radius rods, or 4 bar all of them try to twist the axle on a one wheel vertical displacement. If you happen to look at midget or sprint car front locating set ups you will see that they run parallel rods on one side, usually the left, of the axle and a single locating rod on the other. This arrangement eliminates the attempted twisting of the axle on one wheel vertical displacement situations, i.e. bumps. One of the challenges for this type of setup if you are mounting the steering rack to the axle, is that the steering link can be in the way of the single locating rod. This can be over come with some inventive design. I agree with your desire to have 1.5-2 inches of travel and as ggl205 (the other John) said having the shocks/springs located close to the center line does reduce shock travel in the one wheel travel situation, but not in the total front travel, both wheels.
Rex