1.) drill new holes 1 1/2" higher to raise the chip pan up a bit, can run at higher temps without scorching the chips and chips smoke longer equalling less times door is opened leading to heat loss.
2.) Drill new holes to hold a 5th rack just a bit over the chip tray. I now have 6 foil wrapped bricks arranged on this 5th rack that allow heat and smoke to go around all 4 sides as well as straight up the middle. Bricks are much better at holding and returning chamber to set temp when opening doors. If you want a water pan you can get disposable 3 packs of 10x12" aluminum pans at Smart and Final or the grocery store for 1.99. and place on top of the bricks to catch drippings or steam the chamber. Bonus...no nasty soot covered water pan to clean, just pour out your drippings and toss the dirty pan into the recycling can.
3.) I used a food grade RTV type sealant to seal the chamber better, works ok but is starting to fall off, going to replace soon with 3/8 fiberglass door gasket. With what I have now I can maintain temps as high as 365(verified) if I need that high.
4.) drilled new holes in between all of the stock rack holes in addition to above the last set of rack holes for better rack placement for bigger chunks of meat.
5.) Future, going to have aluminum panels cut and riveted to the smoker legs to better block wind.