After four years of running the original KiPros we are investigating upgrading to the KiPro Racks. Has anyone experienced any heat related issues with the rack version? How many units have you put into a case and how much space between? I see photos of units stacked right up against each other and having had heat issues with the originals, I am curious whether this is a good idea. Currently thinking 5 per case with one rack unit in between each one. Anyone with multiple units in a single case care to chime in?