I would upgrade.

A fully stalled standard servo can draw up to 2 amps of power from the batteries, far greater than battery capacity and causing a receiver reboot.

Of course this NORMALLY does not happen in a properly configured plane... but it does indicate just how much each servo can draw when there is a load placed on the servo, due to air, binding, etc.

With 4-5 servos I might stick with that pack, knowing that I should check it after 4 flights and likely recharge after 5-6 flights.

With seven servos I'll go with a higher capacity pack and opt for the higher voltage for the Spektrum/DSM2 receiver and to get faster servo response.