Lost the control nob and the louver to which it is attached down the RH side vent down into the duct work. Have tried various hooks, two sided tape attached to a wire, and combinations of shop vac tubing attachments, leaf blower blowing in the LH side alone and in sync with the shop vac on the RH side. Without an inspection camera to at least see the problem I believe it is now located in the middle of the cross duct. Perhaps it is now time to either leave it or access the bottom duct work to remove it. What does it entail to drop the duct at the bottom? Could it damage the system if left there?