The dimensions for the V-Racks, from which the FreeLoaders ($(79.00 each side) hang and which are included in the big Dummy LongTail kit but otherwise sold separately (58.00 for a pair) are 15" high and 30 " from out side of tube inserts (1"diameter) at the base and 26" from curve to curve across the top. (not the most accurate measurements but they are an odd shape) THe Vracks insert into the Skyward looking opening on the rear of the frame. The FreeLoader bags are like a couple of big Burritos and you can fit things up to a foot wide in them. Otherwise the hang down from the racks about 15" and hit about 1/2 way down the wheel protecting your load from the spokes.
I hope this helps.