A friend of mine on the island, Brad Roter, introduced me to two of his island friends who have a lot of experience working with bamboo: Andy Royer who imports bamboo and Marcus McNabb who builds with it. These guys have a lot of advice to offer and I'm sure I'll be consulting them as the project develops.
I'm going to explore a lashing technique that may allow me to abandon the bolted connections and still allow the sections to be pre-built and collapsed for travel to the Playa. It's somewhat based off the rubber band technique used by Antoon Versteegde on his sculptures. My first idea was to use Thera-band strips - I can get them in 50 yard rolls in my favorite color: black. The color of the band indicates its strength, black being one of the stronger versions. Another material possibility is recycled bicycle innertubes - although I think they may have a shorter life span under the sun. Experiments to commence soon.
I'm also exploring the idea of eliminating the 4 inner poles of the shade structure and running the guy lines from a floating ring that would be hung just below the top of the first tower section. I believe this technique will impart very little horizontal stress on the tower, instead pressing it down into the earth. Experiments required . . .