If you look at the pic of the stove you can get an idea of the room above the tubes. 1.5in or so. I've been so focused on what to do that I haven't really thought about how to do it. Drilling those tubes from inside the stove is a challenge at best. I can only see three of the four tubes. I'll have to use an angle drill and mirror to get that first one. Still a lot more fun than just buying a new stove. I'll probably install a thermocouple between two of the tubes since I don't have a window. I should be able to detect the secondary burn that way.