I have an FX Wildcat MK2 in .25. I have put in a Huma reg set at 150. Installed high flow port and high flow pellet probe. I am able to get around 900 fps with 34 gr pellets.I thought I may get up to 950 fps so I could shoot some slugs. It seems difficult to get the exact hammer spring tension to get 900 plus. Any thoughts? New spring? Heavier hammer? ???