gcardinal,
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I would not use a self standing monopod. It would be tragic if the rig fell over. Keeping your hand on a the camera when using a regular monopod is a less risky choice and will keep the camera very steady.
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The Sigma 8mm lens is plenty sharp. Here is my latest set, all shot with the NEX-5/Sigma 8mm
http://www.dlsphoto.net/Yosemite2011/Yosemite2011.htm. The lens adapter does not allow the lens to communicate with the body. This is no big deal since most all panoramas are shot in full manual mode anyway.
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As I have learned, overall quality of the finished panorama is more than just lens selection. An ineffecient workflow can kill a pano.
Dennis