Chris
Actually the best way to insulate the roof would be as they do in commercial roof applications by laying Insulmesh over your roof supports then laying Anticon Blanket & Foil over the mesh fix your clips and then you roof sheet.
This would really save you a lot of difficult work later on. If you don't put the insulation in I would a least put the foil in because when you close the carport in you are going to have condensation problems.