My original 1.5W panel was just about up to the job, but marginal. I had one weekend where the depth sounder went blank towards the end of the second day. From what I read recently in Practical Boat Owner Magazine, it seemed that a 5W panel should suffice. I looked at various options and Sunshine Solar were offering a 10W panel at the same price as a 5W for that week so I took the plunge for that. I am planning to instal navigation lights at some stage, so the extra power might be useful.
The panel was delivered in under 24 hours, but they forgot to put in the regulator. That came 24 hours later. The regulator is cheap, rated up to 100W and from my point of view was perfect, as it had three wired in connectors so I didn't have to figure out which wire went where. It all just plugged together and matched the existing battery connector.
All the cables run through self adhesive mini-ducting, which seems to work very well and is hardly visible, but easy to change.. One change not on the photo. The ducting runs under the centre board up-haul, which chafes it. I have glued a stainless steel anti chafe strip over this to make sure neither the rope nor the cable rubs through. When I plugged in the panel, a little "charging" LED lit up, which was very rewarding. It glowed until remarkably late in the evening, even after the sun had just set, but how much power it generates then I have no idea. Now just to see if it does the job.