I decided to rack mount my GK Fusion 550 and got a great deal on a 6 space case. The head is a 3 space unit and the owners manual calls for 1.75" or one ru above and below the head. Is that just being overly cautious or a common practice? I have never rack mounted a head before but bass rigs I have seen use every available space for power conditioners, compressors and tuners... I don't know that I will include each of those things in my rig but it would be nice to have the option with my 6 space unit instead of having to buy a larger one.