I'm interested in a roll film back mainly for macro photography. Looking at B&H's website, it appears as though the Arca Swiss 6x9 roll film back is just a rebadged Horseman with an extra $250 added. Exactly what are you getting for that extra $250. Does Arca make any mods for better film flatness? Or tighter tolerances on the position of the film plane when the back is attached to Arca Swiss cameras?