Prototypes - chopping board variety
An update on this thread.
I've not been able to find HDPE sheets at a reasonable price, so ended up trying Ikea chopping boards.
The blue ones are around 2 mm thick and are too thin to hold any shape - not recommended. The red ones are 6mm, and do hold shape after heating. My heat gun packed it in so these were shaped in front of a heater - I'd recommend a bit more curve. They are held together with cable ties and I'll fit better straps or clips to hang off the safety rope.
Not the most elegant, but they do seem to work and kept a lot of crap off the tubes.