Put together a 2240 and have been working with a prototype 2260 HiPac.
there just isn't a whole lot of volume, so long shot counts aren't likely to happen at higher energy levels. Have to pretty much decide what compromise between power and shot count you are willing to live with. I personally picked 15 shots inside of 25fps variation, but your requirements can certainly be different.
I do use a lightened striker, which does seem to be more air efficent.
the strength of the striker hit to the valve sets the pressure level it runs best at (the sweet spot). Sweet spot my be short, but there are a spots where vel. stops climbing, levels off, and then falls.
Can lower the velocity and extend shot count by strangling off the transfer port (will still have about the same pressure level for the sweet spot, the vel. will just be lower).
To get those 15 shots, the 10" .177 2240 (started life as a 2300s) runs at 120BAR and 6 - 6.5 foot pounds.
The 2260 gets it's 15 shots at 120bar and 17 foot pounds.
Might be able to boost fill pressure, increase the striker hit, and strangle off the transfer port even more and end up at 20 good shots at about the same speed/variation... but my goal was 15 and I'll leave more experimentation until I get bored.
Have to say, the up-down-up-down tendency of your shot string isn't making tuning easy. Try a differnt pellet and see if it still gives those odd low/odd high shots. If it does, would have to look at the sear dragging the striker as a possible casue.