John Calvert is very helpful! I have been on the phone with him several times, on his dime. I had Caltracs with stock six leaf springs. Traction was better but not good enough when track conditions sucked. Most of my racing is on street nights. He gave me several ideas to try before he would sell me his springs. He didn't want to sell me springs and be unhappy if they didn't help. After I corrected the other problems I bought the Caltrac Monoleaf springs. Wow! I haven't spun the tires since I put the Monoleafs on. I even made a pass in a light drizzle and didn't spin. I sent him an e-mail telling him how happy I was. I included pics, video and results. He called me again because he wasn't happy with the 60' times varying between 1.62 and 1.67... He gave me a few more ideas!
PS. Bill from BigBlockDart.com was very helpful too. Any improvements that came up he exchanged components as needed.