Insulation, Radiant and Vapor Barriers - a quirk about insulating my garage

I have a garage with 2x4 construction. At one end of my garage i have a a glorified 'shelf that was built about 2-1/2 feet away from the ceiling just for storage purposes. It was built by running 2 2x4 plates along two of the garage's walls (paralell to the floor)and is supported at the 4th corner by a jack post into the floor. Now my problem comes at the 2 plates running along the walls. Can I get away with insulating behind the two plates with out taking them down. this of course does not pose a problem with insulating as the studs behind the plate are accessible but with running a vapour barrier as it wont be continous. could I seal the vapour barrier at both sides of the plate or wil i still develop a moisture problem. I do intend to sheet thewalls with 1/4' aspenite at least up to the level of the loft. Any help would be a godsend thx.