managing two part urethane foam

Barry
"Depending on the loading, it is difficult to transfer respective large loads into thin material. Not impossible but it will cost you weight. "

I used to build bicycle frames, and we used double butted tubing - thicker at the ends, where the stresses were highest. The concept of a stress riser has stayed with me. If one could find telescoping tubing with close tolerances, one could bond in tubes (inside or outside) to support extra loads. Staggering and tapering to spread stress.

that is a really good point.

Gentlemen, thankyou for your advice, I feel much better informed on this matter and will abandon the idea - at least for masts.