Maybe be careful with opening up the transfer port, as it's not that hard to get these going above 6 ft/lb in .22 caliber. Those are more things I would do with a stock 2250 to squeeze a bit more power out of it.
Bear in mind the more volume you create inside the valve, the more gas it will use. The internal volume and the valve return spring are the main factors controlling efficiency and gas use. Adjusting the hammer spring on its own will change power, but will not necessarily give you more shots per fill.
Also a lighter hammer spring will give you a slightly longer lock time.
The 2240 I have just finished modding is getting 35 to 40 (I haven't shot it to empty yet so it may well get a few more) 5.01ft/lb shots from a cartridge, in .177 caliber.
I was going for a good compromise between efficiency and power.
That has the springs set up like I outlined above, with a wider transfer port (because .177 is less efficient I wasn't worried about it going over) and balanced valve and hammer springs. It also has a steel breech with a hollow probe, which further increases efficiency, but the cost of this part would buy quite a few CO2 capsules!