How are 'Classic' workunits(bpm) maintained once Landmark is activated?

    We have recently installed Landmark in our test environment and have activated the federation of users.  We have also set the PF flag and flipped the switch to process the flows on landmark. I am currently in the process of writing a flow for the landmark side to delete all of our approval wu's once they have completed and are older than 30 days.  What I've run into though is, even though the flows are all running though Landmark; 'classic' workunits are still being generated in the bpm administrator.  I understand that parts of 'PF' still run and manage data on the Lawson side, while other parts are now handled on the Landmark side.  Since we have activated the flows to run on the Landmark side, I was viewing it as an 'all one way or nothing' environment. Can we run 'scheduled flows' on the Lawson side and the Landmark side at the same time; specifically the one that uses the custom activity java bean to MoveWorkunitsToHistory? Our classic workunits appear to be stuck in status's of 25 (Triggered in LPS) and 26 (cancel initiated in LPS) and are never getting to a completed or cancel completed state, therefore they are accumulating. I will need to have a way of removing these.  I tried adding a processing loop to my landmark PF(using the lawson transaction query) to delete the classic workunits that are in the bpm, but I'm getting 'Classic WU 61,533 not found', 'can't delete due to error msg' and 'can't delete due to variables'.  Could someone please give me a 'background' explaination on how the PF's interact between Lawson and Landmark?  What have others done to handle this situation?