The top-of-pole mount offers excellent functionality for getting the maximum performance out of your solar panel. The closer the surface of the panel is to being perpendicular to the rays of the sun the higher the performance (amps output). Thus, the panel needs to be both tilted and rotated. I have found that adjusting an 85 watt panel 3-4 times a day will achieve power generation of up to 40 amp-hours on a clear day on the Great Lakes.
A panel mount should be adjustable easily without the use of tools. Our panel mount provides 13 tilt positions by simply pulling a pin, tilting the panel and replacing the pin. The panel, which is atop our crane pole can be rotated 360 degrees. We provide a pole locking mechanism to keep the pole from rotating on a windy day and have found that using the mechanism as a brake to limit free rotation of the pole works well.
As shown in the picture, our pole is mounted to the stern rail away from the boom so there is nothing to cast a shadow on the panel. Shadows can significantly reduce the efficiency of a solar panel. The pole is mounted high enough to clear the bimini yet easy enough to reach to adjust the angle to the sun.
My sense is that the 120 watt solar panel is about the maximum size
(31" X 48") to mount on the top of a pole such as ours. The limiting factor is the strength of the stern rails that stabilize the pole. A larger panel would require bracing struts from the pole to the deck. Clearly this is possible but I would recommend mounting larger panels to a frame above the bimini, on dinghy davits or directly to the stern rail.
Pro and Cons:
Top of pole mount
Pros: Easily adjusted for best sun angle, clear of shadows, out of the way.
Cons: Limited size of panel that can be pole mounted.
Bimini frame panel mount
Pros: Can mount large panels, out of the way.
Cons: Cannot easily adjust for best sun angle, often have shadows cast by the boom, back stay or topping lift.