I have installed two panels on "trawlers" recently.
The first was for my buddy's CHB 45 pilothouse. Above the pilothouse and forward of the fly bridge is a nice flat area that could hold 2-200 watt panels. It is open to the sun except when it gets down to 45 degrees and is to the aft of the boat where the fly bridge bimini shades it.
We used aluminum L shaped brackets to support it off of the roof for ventilation and glued the brackets down with West System epoxy and bolted them to the frame of the panels. We then ran two 12 gauge cables, one for each panel down to a convenient spot inside where we tied into a 45 amp Blue Sky MPPT controller. From the output of the controller we ran #6 cable down to the battery through a 50 amp fuse near the battery.
The system will put out almost 30 amps at 12V when the sun is overhead and makes about 120+ amp hours each day. Since that boat has propane refrigeration, 120 AH will fully cover my buddy's needs even with a few cloudy days each week.
The other system was a simple 100 watt panel that I mounted on my Mainship Pilot 34 to charge up the batteries after getting back to the mooring from cruising and keep them topped off. I had at least a week to recharge so I didn't need a big, powerful system like on the CHB. Plus I wasn't living aboard so even on week long cruises I was motoring to our next anchorage every other day so the batteries pretty well got recharged from the propulsion engine.
The system consists of a 100 watt panel with hardware store rubber feet mounted on the corners. It just sits on the roof of the hardtop P34. I cut off the MC4 connectors and spliced #12 wire and ran it down the side, through an air vent and into the engine room. I connected it to a Morningstar 10A PWM controller and then to the battery through a 15 amp fuse.
That system will put out abut 5 amps (you lose another 15% with a PWM controller but I didn't care) at noon and charges about 25 amp hours on a sunny day. It works fine to top off my 220 AH GC house bank.
David