The only tubes I've seen set alight, weren't properly mounted and as a result, had fallen onto the exhaust.
Before fitting the tubes, compress them as far as possible before cutting them to length (if at all necessary) usually they fit without cutting. This way the tubes will never fall off, if you still don't trust it, just use some tie-raps to mount them on the adjuster cable and the flat metal strip near the handbrake.
For the places that get rubbed trough, you could maybe tape or glue a metal plate onto the tube.
The foam inside in the original tubing is essential in absorbing part of the noise.

Somebody suggested running a wire through the middle screwed to the heat exchanger and heater duct which will stop it coming off.

I put old vacuum pipe up the inside of originals to stop them collapsing internally but also killing the noise, I also have two computer fans in the bulkhead inlets to blow some air over the screen initially..

Well, I managed to line the new neoprene hoses last night. Small ones with a length of hollowed out swimming woggle and the big ones with some high temp spray adhesive and some packaging foam sheet.
First test show the air flow is amazing, judging by the amount of crap that blew out of the window vents.
Full test tonight!

I'm still swithering about returning the stuff i got and just sticking with the originl tube but doing something more to secure them... any more results to post?

50 mile round trip, it's ace