twinkle, looking at the pics I assume your using a crossed drag link steering set up??
As for the rear wheel, I am putting the 26 inch on as changing the wheel size would require too many mods such as moving the center pull brake assembly or moving the drop outs 3 inches which would change the geometry of the rear triangle thus affecting the suspension movement arc, maybe.
As for loading, yes age has caught up with me as well, but using a pick up truck with a ramp would be easier than on top of a car.
Studying the steering set up in the Hellbent cycles pdf
on page 19. Lots of good info in that pdf .
Still contemplating on using a mid drive setup as it would prevent the chain line from the BB w/ pedals to the rear wheel from changing in a large arc.