Hmmm....maybe a pair of replacement handles for post hole diggers. The strong wooden dowels covered with fiberglass. Not light but very strong.
In the diagram it looks like you have the poles lashed to the trees, attached very close to the tree trunk. Some other straps wrap around the back side of the trees and end up at the pole tips. Could you replace those straps with a pair of ratchet straps. This way, once you get the hammocks set up you can crank up the tension to help put more of a compressional than a bending load on the poles (like a spring pre-load).
Definitely not an engineer.....but I did stay at a Holiday Inn Express one time ;-)