After updating the requested rate for messages, it seems that in the SITL it periodically ramps up to the requested rate and then reverts to the original rate. For example if I change the attitude update rate to something like 10Hz it will periodically get up to 10Hz but then ramp back to 4Hz. I have tested this using both custom software and Mission Planner. Each behavior is the same per SITL, but works fine in the real world. Is this something I can change in a setting somewhere or overcome?
Both MP and Mavproxy set the rates to 4Hz automatically unless you explicitly tell them not to.
So start MavProxy with --stream-rate=-1 or something like that.