Idea with inspiration from my latest project.
It will require edge binding if not on all the foot side then at least 5”-6” past the foot box area (C) in both directions.
In my latest project I made the pleats 1cm (3/8”) 5cm (2”) apart.
I can’t tell you how big you should make it or where to place it because it’s about preference.
You want 16cm more material for the feet and 1cm pleats. Then A should be 16 cm and you have to make 8 pleats. A pleat uses 2x material.
From experience I would start approx 4” before my feet and work up towards the middle of the hammock with 2” apart.
The fabric sides has to be hemmed because of strength at the seams. You can test it without the edge binding but you have to be careful not to overload the edge. Let’s say you want a tight edge (not floppy) then reduce measurement A with 1-2 pleat.
pleats foot box.png Pleats.png
This picture is from another project but it shows the result.