So...by the deafening silence I must assume that the correct answer is that Crimson 15.11.1 does not support display of any Custom Resolution created with the Custom Resolution utility in the Crimson drivers. I was afraid this might be the case, but just wanted to touch base about that to be sure.
In all seriousness, I hope that AMD doesn't take too long to correct this fundamental omission from its Crimson drivers. GPU drivers need Windows display resolution support, including support for custom displays created with the brand-new custom resolution utility built into Crimson (would have thought that would have been self-evident.)
yup I have same problem as crimson does not give me 60hz in 1440p or 4k on my r9 290 and samsung tv old drivers did ughhh.