yes, R9-290 and R9-290X are more difficult to be set.
I am testing with --thread-concurrency 8192 and --gpu-memclock 1250 directly inside sgminer.conf and it seems more stable then before... more tests will come out in the following hours...
I'll keep you informed
thread-concurrency doesn't affect much NIST5-performance (check the source code) I would not touch it. Play with thread-concurrency only bring you 1% more in my experience.
Important is delete all the *.bin file in sgminer-nist5 and set proper clock, intensity.