I have a Coalbrookdale - Much Wenlock coal/wood stove (English import). Over the last 25 years I have been burning nut coal and occasionally wood. The stove is in excellent shape but I have switched to burning more wood and feel that the combo design does not do well for efficient wood burning. I decided to make some modifications with two goals in mind, increase wood burning efficiency and avoid modifications that could not be reversed if it didn't work out. First step was to lift out the shaker grates and replace them with a solid steel plate. This plate sits across the bottom of the stove over the ash tray. Intake air enters the stove through a control on the ash pan door. Second step was to install secondary burn tubes along the top baffle. Air feed to these tubes is from under the steel plate, utilizing the air entering through the ash pan door. This modification was fairly easy to do using 1/2 inch threaded steel pipe. No permanent changes were made to the stove itself. You can see from the pictures it is a free standing insert so I could easily convert the stove back to coal burning. I fired it up last night and had mixed results. The wood now burns in it's ash and gives me a longer burn per load. The disappointment was the secondary burn tubes. I could only see one of the air holes on the burn tubes producing flames. It was the middle air hole on the tube, hottest spot. My guess is there is not enough air coming up and out of the burn tubes. Both the firebox and burn tubes share the air entering in under the steel plate. I have no way to control how much air goes to each component. Does anyone have additionhal thoughts on what may be happening here? Any suggestions for improvement would be appreciated.