Changing SerDes speed on the V4FX RocketIO

Has anyone been able to dynamically change the SerDes speed on the V4FX
RocketIO. I've been able to get the RocketIO to operate correctly at both
SDR rates (2.5GHz) and DDR (5GHz) rates using static parameters but when I
try to change the speed dynamically the RocketIO enter a state where they
never lock up at any speed. The only way to get them to operate again is
to reload the bit stream. 

In simulation everything works. I diffed the wrappers generated by Coregen
1.1 for the SDR and DDR rates to determine which parameters to change. I
used a simulator to determine the values for each of the relevant
parameter registers in the MGTAs and MGTBs. Writing the registers in
simulation works fine but in real hardware it doesn't work at all.

Has anyone succeeded in getting this to work? Are there any steps that I'm
missing?