with this one it looks like you could put a deck on the top bar to stand on ad really tall handle bars it would be like an adult scooter maybe with smaller wheels to get the bottom of the "bike" close to the ground it looks sweet tho
Dropping to a 24" will gain you an inch, shorter cranks could gain you an inch, curving the forks out some more would gain another inch, probably going to need at least two if not all three to get the room you need...
I say relocate that crank tube to the top part of the lower most down tube bend, that way your chain alignment will be better above and below the chain stay and you will also have better front wheel clearance with the pedals.
Barnbikes I like seeing someone else's perspective on stretching out a frame. You are doing a fine job. I had to overcome the some of the same obstacles on my stretch cruiser. I'll be watching to see what you do next.