I haven't used Tonkin cane as yet, can't help there. I have used Moso, it splits readily, it may be ok for a trailer though.

I haven't heard about using expanding foam.
A few of the things I've read about are Polyester amide polyol, and lining the inside of the pole with carbon fiber.

Google up Polyester amide polyol, and you will find a bunch of articles about strengthening bamboo.
For lining the inside of the pole (haven't had the time yet) I plan on using pre-preg carbon cloth laid on a 90º bias to the bamboo's fibers, and cutting an inter tube (and then glueing the ends shut so I have a straight length and not a doughnut) to use as the bladder to press the carbon to the bamboo's interior surface.