Extend to with in 3" of the grate
I used rolled aluminum flashing to extend the tube down to the grate on mine.
Probably if you just added a heat deflector at the entrance to the cooking chamber from the firebox you would see a big difference. The angled piece of steel will force the heat and smoke down and into the center of the pit before it begins it's rise to the exhaust pipe. Tuning plates are great to have, though usually they aren't necessary on a smaller pit and normally a builder only puts them in if they're requested by the customer but when they are working in conjunction with the deflector you gain tremendous control over heat distribution. Heat exits the firebox, is forced down under the tuning plates and gradually rises through the gaps between the plates. You can even out the temp from side to side or create hot and cool spots as you wish. I actually prefer a conventional set up like that to the reverse flow design just because of the versatility that you get from it.
