This could be quite a way off, to be honest. I've had my window unit installed for a few hours today. There has been a difference. Not quite the difference that I had hoped, however.
When I started, the temperature in the galley was 104F and 97.4 in the bedroom. After half an hour, the galley was 102F and the bedroom rose to 99F. After a further hour, the galley was 100F and the bedroom was 97F. Outside the temperature on the second look was 89F according to Google.
Looking at two possible sites to install my cool air intake, it seems that on one side I'd be over the fuel tank and over the battery compartment on the other. Neither is therefore a truly desirable location. Given that the window unit does not have much effect, I'm not that inclined to commence work on either solution until I find a better solution.
Clearly the only work I can get on with at the moment is filling the hole in the bedroom floor. That's almost straightforward. It needs a 7"x5" plate riveted on from the underside. I can then cut the plywood on top out to a larger size and replace that too. It's in a closet so it won't be load bearing.
What the hillbillies did was all good ideas. The execution was poor though. Poorer than that was the question of longevity. Their stuff didn't last long.
Clearly I need some form of ventilation for cool air. How to achieve that is a bit of a mystery. There is a roof vent but I have a feeling it's more for exhaust than induction. I have no idea if there's even a fan connected to it. That could be a solution... Put a fan in there and use it to blow warm air out. My heat removing fans are working.
Today I saw online somebody's suggestion that using a single diode and a battery one could use the solar panels to keep the fan going. I'm not sure the panels really generate enough power for that though! As I always say... Keep it simple!
My goal is to keep the internal temperature the same as the outside temperature. Thus far I have not seen the excessive temperatures of last year but August and September are not yet done. Last year, the high point was 140F!
It would be possible to use my motor home as long as I stay out of it during the very hottest parts of the day. That's doable but means no very early nights etc. It wouldn't be possible to live in it and do night work, for example. I do have ideas for cooling via other methods, particularly a modified evaporative cooler.