Game 1:
gameID=14704Game 2:
gameID=14705Game 3:
gameID=14970Game 4:
gameID=15070^That's the correct link for game 4; the other was cancelled.
It seems that the central powers have a slight advantage in gunboat AC due to the fact that they are harder to suprise attack - however, from the testgame (and the few press games that have happened here) it seems that, with an evenly matched set of players, it's the corner ones (England and Turkey) that have the slight advantage, due to their greater mobility.
That said, it's not a particularly unbalanced variant - any power can do well if played well. The one exception seems to be England in gunboat, because everyone who is doing badly seems to seek refuge there. If you can predict and block these 'jumps', England is quite a strong country too.