Derek Giddings is a shooter for the H&K Shooting Team. Check out the MP5 he is using. It is setup purposefully for racing.
The optic is set high as well as the stock.
The position of the stock actually lowers the bore of the barrel helping in minimizing muzzle climb. If low bore axis works in handguns, it should work well for PCC. With the optic set that high it allows for a clearer sight picture. Cowitnessing Irons on an MP5 can get a little crowded and since this is a purpose built race gun, speed is the priority.