Half the area under my F150 Super Cab rear seat is the sound system amplifier setup which is a very large metal box. On the other side of the rear seat area are my two way radio main units, 1000 Watt Power Inverter and 12VDC distribution and fuse panel. All of these items are bolted down under the rear seat floor area.
There is no way I could just remove the rear seats... It folds up very nice to the rear seat backing and I have a very large area in the back seat area to store all the things you listed. I can even safely stow away my 2KW Generator and large tool boxes here as well... With the two rear side half doors opened and the back seats folded up you can almost run thru the back area and not slow down haha...
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Roy Ken