Yes, with the 20/1.7 (or any Lumix-type lens) you can pre-set the aperture and then reverse it. On the whole, usually easier to just use all-manual legacy lenses, although as I said the 20/1.7 is ridiculously sharp.
The link in my above thread is a good MTF-52mm reversing ring
http://fotodiox-inc.amazonwebstore....src=froogle&utm_medium=CSE&utm_source=froogle
I have Panasonic 14-42mm lens so I can use the MTF-52mm reversing ring. Thanks for the great info.