Hey guys
See the Release Notes of 7500 R6701 Page 6:
"SFP+ Direct Attach Cables are not recommended for use as IRF connections because failover and recovery times are extended when this form of copper connection is use. Optical IRF connections are recommended to optimize IRF failure, recovery and convergence times."
For the the 5800 it's okay, for 7500 I use only fiber.
br
Manuel