Does xpmclient can control over 10 GPUs on 1 system?
this utility would crash if assign over 10 GPUs, is this a openCL limitation or can be fix by xpmclient next ver?
10GPUs? 5xHD7990 or what?

It's not OpenCL limitation.. may be bug in xpmclient. I don't have access to rig with so much GPUs, can't test that.
Unfortunately, i needed to hack the xpmclient.cpp file to remove the test after the line 1251 about incompatible configuration :
Do you try remove kernel.bin and recompile kernel ?