I need to know how deep of an equipment rack is needed when using the rear rack kits for a SmartPack portable. In the past I purchased a rack based on the demensions of the Smartpack as listed on the Datasheet but it didn't account for the rear rack kit. Of course I can't find my notes about what size rack I wound up getting. I have checked the Datasheet, installation manual and operation manuals but it doesn't appear to be listed anywhere. Thanks.