Sounds like you have got yourself a hot rod. Just remember that more milliamps means longer flight times which equals engine heat. I wouldn't hold it full throttle for extended periods. You are ok on more milliamps but don't exceed the recommended voltage which I think is 8.4 volts. Another thing to keep in mind is bigger NiCads=more weight. Don't get into the circle of bigger motor/bigger battery as the additional weight cancles out the additional power. The wings on the aerobird aren't reenforced (as stock) so be careful with all that power and weight or they might fold.
Have you considered Lipo's? They are the ticket for electric planes. A fraction of the weight of Nicads and gobs of power. The down side is the are expensive and require special chargers.

WCB