I have a new Littman Single Shot RF 4x5 camera with 150 APO Symar lens. I want to do environmental portraits with color neg film and make large prints (20x24, 30x40 and 40x60). To avoid fuss in the field, I'm considering the Polaroid 545i back, to use with both Kodak and Fuji Readyloads and Quickloads. I've been told for absolutely critical applications, I should use the manufacturer's loading device. I'd prefer the portability of the Polaroid. Has anyone used the 545i with either the Kodak or Fuji Ready/Quick Loads and done large blowups? Will I lose sharpness, focus, etc. doing this? Also, has anyone tested the new (still hard to get) Kodak Single Sheet Ready Load back with Fuji Quickloads? Are the results critically sharp? Thanks, Bill Jorden (billjorde