Well I used to have my rig set up in the photo below.... I never had any problems with it, although it was just a bedroom rig (how overkill!). If you are going to balance the head on the FX, just make sure that the flightcase is nice and sturdy, so the weight of the head doesn't make it collapse :) It should be fine though, the flightcase in the photo was cheap and a bit cr@p, and it is still with us today, albeit not in the same setup!
Edit: just realised that photo is over 4 years old... just seems like yesterday, though!