KF2 ride height problem

[felix777]

I have just built my KF2, and have discovered a problem with it. I built it with the kit springs, and have discovered that at the rear of the car the ride height will not go lower than 19mm, even though the shock collars are wound all the way up. I am not running much rebound and the shocks are on the front as I am waiting for the upper transmission housing to come into stock. I will attach a picture. So could anyone possibly help me with this? Cheers