The VSC changer should screw right off!
The verticle 12 gram changer is a "Rat Attack" style of changer. It fits into ANY ASA. The verticle adapter is an ASA, and it should just slip right on there.
Alternatively, you can get a bottom line kit from CCI for a little cash, and it'll screw into the vert feed you already have. I converted my Phantom to vert feed with only a few problems (bad seals...) but that's easily fixed.
But, yeah, the 12 gram changer should screw out of the vert ASA, no wrenches needed. And, 4 ounce tank is a GOOD choice!
Center feed, 9 inche barrel, nice T-stock, 4 ounce tank, Speedball Diety.
-Tyger