So the basic idea is to insulate your cooker as much as possible to retain heat. Do you adjust the height of the walls of the maze to compensate for larger cookers?
Well its an insulated cabinet so it's well insulated. I don't think the height is the issue as the bigger cooker would have a bigger/wider/deeper charcoal basket. The maze in a bigger cooker would hold more charcoal so more would be lit to keep a bigger cooker up to temp.
I've made/experimented with several charcoal baskets and mazes. If you want to make one out of metal try aluminum flashing to test with. They are easy to bend and cut and reshape. They also come in sizes to fit most charcoal baskets. They also seem to hold up better than you would think to fire. I still prefer firebricks but they don't fit in my smaller cooker.