Alex tooked at the channel definitions (can be seen in tpchn_C1.par), and noticed the rmid was 0.
However, we had set in testpoint.par the tst system to C-node1 instead of C-node0. The final number inf that and the rmid need to be equal. We have changed this, and the test points appear to be working now.
However, the confusing part is in the tst model, the gds_node_id is set to 1. Apparently, the model starts counting at 1, while the code starts counting at 0, so when you edit the testpoint.par file by hand, you have to subtract one from whatever you set in the model.
In other news, Alex pointed me at a CDS_PARTS.mdl, filters, "IIR FM with controls". Its a light green module with 2 inputs and 2 outputs. While the 2nd set of input and outputs look like they connect to ground, they should be iterpreted by the RCG to do the right thing (although Alex wasn't positive it works, it worth trying it and seeing if the 2nd output corresponds to a usable filter on/off switch to connect to the binary I/O to control analog DW. However, I'm not sure it has the sophistication to wait for a zero crossing or anything like that - at the moment, it just looks like a simple on/off switch based on what filters are on/off.