Tried with the cotton a little higher, more than a little higher, flush with the shelf, behind the shelf... With cotton gods (that seems to work in everything else I have).

That's with 70/30, 75/25 and 80/20.

I should be getting some ss wire soon, so I might give it a go with TC - I honestly can't see much else stopping the eventual burning.

I'll take a pic of mine later, it's had 3 tanks through it (straight glass, the bubble somehow seems to make things even worse).