I am using the passenger seat from the Kawasaki donor as a seat back/back rest on the new trike. The underside of the seat back is formed plastic with four threaded bolt receivers fused into the plastic. These will be used for attaching to an adjustable bracket which will then be mounted to the frame of the trike. (See arrows Photo 1)
Four mounting tabs are cut from angle iron and drilled for bolts and two mounting rails are also cut from angle iron and drilled for bolts. (Photo 2)
An adjuster arm is cut from 1/4″ flat stock and drilled with a series of adjustment holes. This will allow the angle of the seat back to be altered for the most comfortable riding position. (Photo 3)
The tabs, rails and adjustment arms are bolted to the bottom of the seat back. (Photos 4 and 5) The bottom of the seat back rail (on the right in Photo 4) will remain in a fixed location but can be pivoted around its attachment bolt. By selecting different mounting holes the top of the rail (on the left in Photo 4) can be adjusted either forward or backward to provide optimal back support and a comfortable riding angle.
The mounting assembly is taken apart and the two side rails (see red arrows in Photo 6) are positioned and welded to the frame of the rear deck lid.
The mounting hardware can then be reassembled and the seat back bolted in place and adjusted to the desired angle. (Photos 7 and 8)
The cargo case now opens normally from the rear (Photo 9) while the deck lid, cargo case, and seat back can be swung up and open for access to the battery pack and electronics. (Photo 10)