This is an update on my last post about taping a tray ceiling and that awful 135 degree angle. I was having horrible trouble with the joint — keeping it crisp and straight.
I ended using Super Flex No Coat. Strange stuff — the only mud applied over the tape is a skim coat over a paper flange (it’s bedded in thinned mud). However, I’m very pleased with the result. Took me two skim coats and a bit of fussing, but it works as advertised. Costs about $50 for a 100 foot roll.