Rumdog, .....I can't see the link. Sorry.
Freebeard, .....in another career I spent some time as a Plastics Process/Design engineer. With the plastic core made of polyethylene, a strip heater could be used to heat the local area where a bend is to be made. The "Glass Transition Temperature" , the point where the polyethylene is between a solid and semi-viscous processing temperature should be in the neighborhood of 275-310 Deg. F. I'm thinking that this ought to be below the point where the alum. skin would crystalize and work harden. Thoughts? I'm really liking the pictures of your model. It looks something like the Decoliner that the Blastolene brothers did just a few years back.
http://silodrome.com/decoliner-blastolene/