Sounds about right..although from the bottom of the sweet spot to the top is more like 20-25 strokes.
Can play with power by way of the transfer port, although with a small volume the faster it goes the sooner you refill. Easier to get a handle on velocity changes if you think in terms of area of a circle rather than just drill diameter for any transfer port changes.
Co2 hasn't been seriously tested, but would guess in stock form (with the tiny transfer port) speeds would be pretty low (more like BB-SSP speeds..something around 350-400 on a guess).
Went ahead and made a shroud for mine, and upped the speed to about like an R7. Having the front sight mounted on a solidly mounted shroud didn't cause any accuracy loss I can detect (and its a quite accurate little gun).
As a carbine...had not painted the shroud or added the front sight at this point:
As a pistol:
To be honest, as I bought another nice .177 rifle, this one is going back to pistol configuration., the original transfer port getting reinstalled.....open sights and all.