devchander,
on the second system I am using SCXI-1521B's instead of 1520s - but either way the 1520 and 1521b strain inputs are in multiplexed mode.
also, the software "fix" for this was not an option due to the sampling rate necessary for our testing - so if it does work for you it might not be necessary to switch over.
either way - good luck - let me know if you have any other questions.