I like your BLUE SEA feed-through idea
I've been contemplating using PVC Electrical BOXES mounted on the side of the trailer up at the roof line for mine but the UV's may be too much for that over time...
I already use the PVC Electrical Boxes (LOWES) idea for gaining access to the roof area with RG cables and I guess they are surviving ok being in the sun... Having weathertight removable lids sure makes it great for keeping track of the cables... I do the same thing for my 4AWG battery cables at the floor level coming and going to the battery banks...
My goal is to install whatever I come up with to give me around 20AMPs DC Current when in the high sun.
I have already decided to always make my initial DC Charging using the 2KW Honda Generator running my shore power cable to get past the high current phase of 50-60AMPS DC current demand by the batteries for the first charging hour then if I have high sun will allow the panels to finish my charge state until the high sun goes away each... I will always start my run off the batteries with them at their 90% charge state otherwise it will get dark on me around 10PM at night and I have to shut down everthing when I see 12.0VDC on my meter panel. Presently this is occurring at 8AM each morning when I am usually allowed to run my 2KW generator with all of the generator run restriction I usually run into here on the East Side of the USA.
The joys of living out West with all of the vast primitive camping areas available to you sure has its merits... Even our Natl Forrest areas have generator run time restrictions here...
After doing this I may change my mind using this method but for me this is the best for sure method of always starting my day/night run off the batteries with at least the 90% charge state. I will be drawing in the mid 20's amps from 6PM to 11PM with my planned power draw.
Keep us informed on how thing go with your initial solar runs...
Roy Ken