Actually I have a direct fired RIMS set up, so I am constantly recirculating.
Also I sleeved the 1/2" stainless nipple,first with a 1" steel nipple and then a 1 1/4" nipple over that, to shield it.
Set up like this I've never scorched anything, even before I started constantly circulating. (It's probably better not to take the chance of not circulating especially while firing.)
If your interested I could post a couple pictures.