you should be able to get the seal with stove gasket rope siliconed (with high temp food grade silicone) to the lid (that is welded to the bottom of the drum) and the lever clamp would tighten it down. Real interested in how it works.
Drumhead - UDS x 2 & UDG
Keep on Smokin'
KC native missin' KC
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I also support PETA - People Eating Tasty Animals