Merry Christmas by the way. I am responding to try and answer some of your questions for you first of all The foam I used I came across at work it was protective prepackaging in some equipment that had arrived Its not polystyrene you know the stuff that breaks up in to little tiny pieces and gets allover the place This I found this stuff practically indestructible and super light and although it looks like sponge it is not hygroscopic in any way. I used it for its buoyancy property's ,In the hopes that if for some reason I have a disaster one day That it might help to keep it afloat long enough to salvage her ,not like the Titanic lost to the depths forever. of course I do not intend to test this out .,Its only a hope for the best.With regards to the charging jack you have noticed you are correct it will be used for that also ;but it is also a 12volt power supply for my lighting. My superstructure lifts off the hull in one piece and the electrics for the lighting is all fitted in the superstructure so I have a jack plug I simply plug in when fitting the superstructure to the hull. The socket was very cheap and found it here
https://es.aliexpress.com/item/Hembr...6d1929e433c938