While scanning through the source code for the plug-in, I found the terminal switch to enable on-screen debugging. I switched it on and tried moving the spacemouse while the game was running. I continued to get the HIDP_STATUS_INCOMPATIBLE_REPORT_ID error in the output window, but I did see the expected debugging values!
So the data is getting there. I haven’t had sucess yet getting it linked correctly, and I’m still seeing a stream of errors, but it’s encouraging.