With the fluted hammer I used a green valve with red mainspring from an authentic nelson spring kit . I was able to shoot around270 to 280 fps and got a good 35 shots off one 12 gram in the summer . It felt like the hammer was grinding inside the redux snub every time I pumped it so i decided to take it out and keep the spring combo the same . I only lost a few shots but I was able to back out the tpc adjustment quite a bit and made the pump stroke smoother . The lightened hammer was ok but I just prefer the stock hammer weight .
With the setup you are using that sounds like a good amount of shots .