I know this is an Old Post, I did a Google Search and found it so I decided to read it. I've used the Promax metering plates, there is an engineering problem with those plates. They do not seal to the body of the carburetor with the large cavity behind it, the guy at Promax says not to use the little thin plates, well they don't cover the Promax metering plate anyway, the last six pack I built I use AED jettable metering plates and they seal up fine, I saw on this thread someone posted about jettable non-billit metering plates, are those available, I've never seen them before?