Using available tools (I simply used the knife off my Leatherman multitool to carve and punch), cut a hole in the rear of the air tank. This opens up the pilot volume. The range tab is the blast button, while the whitish disc is the check valve for the pump. NO MATTER WHAT YOU DO, DO NOT IMPEDE/BLOCK THESE. They're kinda important to blaster function.
I elected to use cheapo plumber's epoxy to fill in the pilot volume. Essentially, I reduced the diameter of that part by about a third. I wold recommend making your hole wide enough to accept a 2/3 circle of PVC (by estimation, possibly 1" SCH. 80 PVC) and then filling around it with the plumber's epoxy. Seal off the hole you cut with the piece you removed, and cover that with some epoxy to make a good seal. Let cure.
Reassemble and slap on your coupler of choice.
Without plugging the pump, the OPV was going of on the second pump. With the pump plugged, a foot of PETG in that PVC sheath, and 1.5" slug darts, I was getting 90' with 4 pumps, and 105' with 5 pumps.
Edited by Buffdaddy, 01 October 2011 - 11:02 PM.