A vent will not even out a firing unless it's only very slightly uneven. The only way to ensure even firings is to modify the load as I described above (which still may not do the job), or to get a kiln with zone control. More thermocouples = even firings. Most brands offer zone control as an upgrade (Skutt, Paragon, etc.), L&L has it as a standard feature. It's well worth the money to have it.
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