I have been using crappy 4 inch soft metal ducting for my red Dragon pre-heater for years. The other day I borrowed another pilots heater hose. It was the internal wire wrapped type covered with some sort of canvas / fabric type of high temp stuff. We had those in the military long ago.
I went to the local boat shops, Nappa and Spenards and they had no idea what I was talking about.
Do you city folks up in Los Anchorage have a place to buy that sort of thing?? Amazon.com only has the orange scat tubing and I am not so sure that is high enough temp.