Dynamice Sub procs with multi values CDT's

hi all,

I'm currently playing with sub processes and the ability to dynamically start a given number of them (MNI), but I'm having a few problems. I'm not sure if's it a gap in my Appian knowledge or a mis understanding of how the product works.

I've created a basic multi-value CDT, 

TEST

fieldA

fieldB

fieldC

This is populated in my master process and so I end up with effectively an array.

fieldA      id1    id2    id3

fieldB      AA    BB     CC

fieldC      DD   EE      FF

I have configured MNI to run a separate instance of the sub proc for each instance in the CDT. So using the above I get 3 instances of my sub proc started. This I'm happy with.

However my issue is with the data. My sub proc has a pv with the same type of the CDT. In the parent process I have mapped the parent CDT to the sub proc pv.

what I was expecting, is that each instance of the sub proc will have it's pv populated with the one instance from the original CDT. i.e

sub proc instance 1 would have id1, instance 2 would have id2 etc. What I'm seeing though is that the full CDT is being mapped over to each instance of the sub proc. 

Any ideas ?