IBT with five runs isn't enough for an stable rig.
Use y-cruncher y-cruncher in stress test mode*, LinX, prime95 or OCCT for more that eight hours for stability.
*Launch the program, press 2, enter, 0, enter, x GB (x being nearly how much RAM your system has free according to task manager), and press enter. The program will periodically indicate how much time has been consumed for the testing.
Then you can call your overclock stable.