What shape is your shot string at the present time?.... Does it start high and decrease as the pressure drops, or does it start low and increase and then fall?.... The hammer spring preload will govern the shape of that curve, so although you will gain fps as you turn the adjustment CCW you may move the peak pressure up so high that you end up with a falling velocity.... Use the hammer spring to shape the curve, and use the port sizes (including the OD of the sail) to set the power, at least initially....Bob
You are not running "stock" port sizes if you have plugged five ports and installed a sail, correct?.... You have severely reduced the airflow by doing both of those mods, which may be the reason for the velocity being lower than you want to achieve.... All I'm saying is that you need to find out the shape of the shot string before you will know where to try and improve the velocity.... Changing the hammer spring preload may not be the correct choice....Bob