Take a pic of your setup.
You have a braided SS line and it is still melting? Is there no way you can re-route that drain line (use an angled AN fitting) such that it does not come into contact with the downpipe (that's why a pic would be helpful)?
I have used the heat sleeve/jacket on a car that the drain and downpipe were in direct contact and it definitely helped (have not melted anything yet). This however is not ideal and I would advise that you periodically check the sleeve and the drain line as those sleeves start to shed their coating when they get too hot. What you can also do is wrap the downpipe itself so that it emits less heat and the metal does not chafe the heat sleeve on the drain.