CC1200: Reducing 40 MHz clock oscillator spur levels

Is there a way to affect 40 MHz clock oscillator spur levels in output by tweaking some internal frequency synthesizer setting? I use external 1W power amplifier and spur levels at +-40 MHz offset from carrier are -70 dBc which is good level, but I would need to reduce them further at least by few dB to get some margin for type approval specification.