I don't know enought about special FX to say whether a rooster tail is possible or not. The only way to make it work that I can think of is write into the config file of the aircraft a position for the effect that is below and behind the aircraft. For example, modify a plane's config file so that it generates a smoke effect 50' below and 50' behind the aircraft. Fly low and hit the "I" key and it might look like the smoke is a rooster tail. It might not. You might be able to tweak some of the settings in the smoke effect and how it's generated to get an effect more like a rooster tail.

The aerobatic teams you saw are really only one flying object. They aren't 4/6 aircraft flying in formation. The designers really pushed gmax to the limit on making them, and I think they did an excellent job, but it's not real formation flying.