Replacing Tape with Tube and adding more Tape:
The bars up the back that meet 1/2 way along a fore/aft tube are the seat back support.
Changing a couple of bars in the helmet area, they came too close together at the front and by the time I put rollbar padding on them they push my head down a long way.
The back will stay in the same point to intersect with the cross above the engine compartment, the front will move down pushing therm further apart, two extra bars will then go from the front down to the where the main hoop and midrail intersect.
Looking at the floor of the riders compartment:
My butt goes pretty much on top of the cross in the middle of the picture, wheeltub is on the right.
Wheeltub:
The two running up the back of the wheeltub will support the top suspension rocker and the handlebar mount.