I think the tamiya springs are too soft for our trucks....they squat even with a empty flat bed trailer on back. I would try to add a few leafs or possible add some shims between the spring mounts and axels to get the frame hight up a little more....
can you shave any metal off the axel so it tucks up more?
This is the same kid of issues as 1:1 trucks have with big floaters on the push axel. They ride about 5" off the pavement. Go over a curb and it touches....
Saw this single wide low pro on rc4wd
http://store.rc4wd.com/LoRider-17-Co...es_p_1506.html