The extension puts the filter down in the fluid. I would try it a quart low and see what it does. A quart low is still 1 quart over stock capacity with the deep pan. You can always add that quart back at any time. It isn't fixing the root cause of the leak but it might help upi diagnose the leak. Just spit balling here. The fluid level with a stock pan and filter is just at or below the gasket surface.
