Gosh, it sure seems we're working on creating the same
suspension setup. I've got underriders on my Mach. Here's a pic:
I can't make any real comments on performance since I've barely driven the car since installing them, basically only about 20 miles total. I chose them because I liked the potential traction benefits and resistance to axle lift on braking.
BTW, here's a list of stuff I've done if you are considering any of it too. Let me know if you've got any questions.
Promotorsports negative wedge kit
Addco sway bars (1" front, 3/4" rear)
PST polygraphite bushings (lower control arm, strut rod, spring perch, sway bar)
NPD 5 leaf mideye rear springs
NPD heavy duty urethane shackle kit
Underrider bars
Global West subframe connectors
Hope it helps...