Yeah, you can add a 1,000-2,200uF capacitor rated for 10v or more on any unused receiver port. This will help provide extra current for those bursts.
Or, use an external, beefier BEC.
Do you really need even that much? The brevity of the bursts and the bursts only being a few amps you should be able to get by with something smaller like a 220, right?
All I ever wanted was an honest weeks pay for an honest days work.