Hi Ned B,
Welcome to 'Foamieland'.
Your design has a few antecedents on the forum here.
A few are:
A very recent one is Standupguy's:
viewtopic.php?f=50&t=43655
He's just finishing up his infill panels. A nice simple
design.
An exemplary one is Sharon's:
viewtopic.php?f=50&t=27313
Really nice and her dual doors - one on the side and
one in the rear are a really GREAT idea.
A really good Foamie example is Aliagtor944's:
viewtopic.php?f=55&t=49879
He is finishing up enough now to make it campable. He's
using fabric for infill sides at the moment but plans
to do solid walls later on.
Also go 5wide as a minimum. Best practice for mpg is to
have the TTT tow profile fit within the tow vehicle's [greatest
or final] cross-section size, [Height and width] or as close
as you can get to it meeting your design needs. The "theory" is:
it just follows through the "hole" in the air that the tow
vehicle has already 'punched' in the air. Building a 5wide body on
the 4wide frame is no big deal. It is done all the time. Just
use a reasonably made floor torsion box to do it. Wheel wells
are not a big deal either, generally less to do than fenders.
A 'slouchy' /'standy' with an aisle to put your feet in when
sitting on the bed, with purpose-sized equipment storage
cubicles, sounds ideal for your needs. Smaller/miscellaneous
frequently used items can be stored in 'modular' plastic bins
set on the aisle floor for travel and stacked up at it's end
when parked. You could also have room for a porta-pottie at
the aisle end if you wanted. looking through all the different
builds can get you inspired/amazed at the various possibilities
for arrangements/floor plans.
Good luck with your move [Where in NY?] and have fun planning
and building once you can start in.
Cheers,
Norm/mezmo