Possibly THE Most Fun Edit I've Made
... And I've made a lot of 'em.
Go to <GroundInfantry Name="Scout_Trooper">. It's the very first listing.
Find the line <LandBehavior>. In that list, change BIKE_LOCOMOTOR to FLYING_LOCOMOTOR
Add a new line: <Min_Speed>3.0</Min_Speed>
Go build some speeder bikes and have fun! ^_^