Imho it is problem with gas flow. With the CA mod you have better separated liquid CO2 from gas CO2 so you have lower velocity than by first shoots with powerlets. Imho you need simply mods for "Low-pressure" - better air flow for the "thin-bodied" power source.
You can dry boost the valve air flow even more. Entlarge the holes in stock valve body - central opening to 6.5mm, four holes to 5.5mm, round the channel bottom into R3.
Or you can Entlarge the hole between of the tubes. Look here: http://invisionfree.com/forums/Stock...howtopic=15792
Or you can solve your velocity problem the other way. In Speed Daemon bolts there are big leaks trought thier velocity adjuster. You can remove the adjuster, seal the entire space with full screw (it is 5/16 UNF lenght 1/2"), teflon tape and tin solder (in the slot for the o-ring) and get rear velocity adjuster (adjusting the velocity trought preload of the hammer spring). After sealing of the Speed Daemon bolt, the velocity of my P68SC in his first 13 shoots increased on average by 45 fps. So when you have 240 fps now... if are 285 fps good enought for you, then I think that you can solve your velocity problem with this mod.