Thanks for the note! I have to slot this into a cabinet in ye olde data center so I'm afraid horizontal is not just a stylish option, but the law! I could probably get the drives to seat without caddies but I always worry about vibration, etc.
Note to mention the scary Frankenbox effect can scare management (though the data center is tucked away in another building away from headquarters, so that's less likely).
Since the caddies are not terribly expensive and I've got the funds budgeted, I'm hoping that will work.