I'm baffle now on what exactly is causing your bouncing off the starting line, but keeping in mind some of the laws of physics that like for every action there is a opposite and equal reaction
With that in mind I would now do like Mike(MrPbody)suggest to find out what is causing the rear of the car to porpoise and unload the rear suspion
The key to good sixty foot times is keeping the car glue to the track during the entire run, not just the last part
Good luck, let us know what you do and the effects on your car