Well after some of you said try ultraflex 325 I thought I would try it. Its def not going well. The issues I'm having is it feels like there's no mud under the taper. I'm tapping it with my finger and some parts sound hollow and some solid. I'm also having a problem getting it sitting on the corner at the right angle. Not sure if this pic shows my issue but once mudded I'm gonna sand through to paper and through to the core to get a nice looking corner. Is there a tool to apply this stuff?