The mods above, minus the thumb tack, improved shot count from 10 to 30 (on 1 CO2 powerlet).
Using 8.44 gr JSB 4.53 mm.
With velocities ranging from 175 to 193 meter per second (192 to 212 ft/s).

Velocities before the mods were around 210 ft/s, so I think the gun is still at its max.
This probably means that I still have CO2 waste, but less than before.

One factor is the huge hammer. 62 grams.
Frakor is going to modify a two power Crosman 180 hammer, which weighs 51 grams.
Otherwise I could drill a hole in the Taiyo hammer, but I'd rather keep that original.

Tinkering with CO2 guns - more fun than any other type, imo.