1. Remove second-seat crankset.
2. Use first seat post for steering column.
3. Mount sling-back chair just ahead of second-seat post.
4. guy-wire front handlebars to rear handlebars.
5. Transfer brake and shift cabling to second-position handlebars.
My main need is for a seat/plans and an articulated handlebar bracket, the rest can be jimmy-rigged pretty easily.
In your post of the list, #4 will require instead of guy wires push rod with tie rod ends...this has been proven to to be more secure. Look up remote steering lwb recumbent. this will give you an idea as to
what to do.