We have 4 panels (see photo) on our Tayana. There are two 85 watt ones aft and two 50 watt ones forward which usually provided all the power we needed (no water maker or refrigeration) during our two year cruise of the Pacific. In fact, the norm while at anchor was that our batteries were usually topped off by about 1pm every day. Underway, they were less effective since one side or the other was usually shaded by the sails. I have seen them pump 13 amps into the batteries, but a more normal charge rate was 9.5 - 10.5 amps. Not having to run the engine or a generator every day just to charge the batteries was really nice. On the other hand, when underway, the forward one had a tendency to trap the jib sheet, especially the leeward one in light winds when the jib would occasionally collapse and refill. Folding the leeward one down as shown in this photo reduced this, but didn't eliminate it completely.

Coupled with the fact that the Tayana has a canoe-like stern and the fact that we had a Monitor wind-vane (wind-vanes are God's gift to cruisers) made it difficult to have davits. There are some owners that have put panels on a tower at the stern (and in fact, our new KP-44 has one), but all things considered, especially the ease and cheapness of the way I made the rail mounts, that was what we decided to do. In retrospect I still think that, for this boat, this is the best mounting method.

FYI, we took a short piece of light line, just long enough to tie a prussic knot around a shroud, then from that, tied a piece of monofiliment fishing line to the outer edge of a panel to hold it up angled to the sun. The fishing line wouldn't cast any shadow on the solar panel.

This photo shows the situation underway quite well. If you look closely, you can see that the starboard ones are in the sun and we have them deployed in the horizontal position while the port ones are in the shade and we've got them folded down.

One of the things I've considered doing is adding an 80 or 100 watt panel just aft of and just under the level of the boom crutch, and above the sunshade. This would normally be shaded by the boom while at anchor (and thus next to useless), but underway, would more often then not be left without any shadows on it.