A little extra piston weight with a steel tophat, sized AA seal, plus some preload on the Maccari/ARH spring on a fitted delrin rear guide gives nice recoil and 670-680 fps with H&N Excite Econ 7,4grs pellets. Thats 7,5fpe, but theres room for some more spacing on this spring.
I'm hoping for a little extra energy when I try JSB's.