depends what type of synth it is. If its an old, nice vintage synth that isnt a moog(moogs are unkillable) there is no safe way to do it right. Old polysynths don't gig well/

But if its a juno sixty up to the most recent models of keyboards, It should be fine in the fight case so long as it doesn't bump around in it. Most of the modern stuff has the surface mounted components on it and they are very robust.