FX Crown hammer adjusting and speed of the JSB kings heavy (MK1)

I had the change and privalige today to shoot a demo fx crown .25 (the gun is not available for sale yet in the Netherlands) and have a question about the settings A through E. It seems that A through E just like the 5 to 1 setting lowers the speed so what is the difference.
At 120-125 bar the regular JSB kings 25,4 grains shot about 900 fps at max hammersetting and max flow (3) The King heavys MK1 only shot at about 788 fps. I increased the pressure to about 130 bar but the speed did not increase indicating to me that the gun is already maxed out so i turned the regulator pressure down to 115 bar resultig in the same speed as mentioned before. I would like to shoot the king heavys to a higher speed.

​Any suggestions are welcome


​Regards,
Jan Peter