Rocket IO : How to put K Characters on LSB of Output Data

Hi All, I am using the Rocket IOs in V2 Pros. My problem is that when i play with the phase of the RefClk, the K character is sometimes output on the MSB and Sometimes on the LSB, (the former throws my whole systems off track, as all subsequent data is misaligned on the byte boundary) Can i force the K char to be output on the LSB of the 16 bit RXDATA path ? How ? Thanks Adarsh