I've done several batches lately, and I found that varying the size of the fish, the brine time, or the temp/cook time can lead to some very different results.
This batch came out amazing. I also smoke it and then refrigerate to eat for breakfast on toast with a little cream cheese and capers (yum).
I use fresh head-end filets with the skin, never the tail as it is too thin and cooks too fast. About 1" thick at it's thickest and perhaps 1.5 to 2 lbs per filet. 4/1 brown sugar to salt ratio overnight for 12 hours. Rinse well and let dry for the pellicle 2-4 hours.
I go Serpentine method with Applewood and Hickory wood splits on top the serpent (perhaps 1/2" to 3/4" wide and 2" long). I use a 2 coal chain on cool days and a stacked 4 coal chain (2x2 stacked) if it is near freezing. I won't bother if it's over 65 degrees outside.
The key for me is to start the fish at about 100-120F and slowly let that temp build to a maximum of 160F. I pull it when the internal probes at 135F. Any higher cook temp or internal temp gives me less moist meat and a harder pellicle. For this cook it was late in the day and about 34F outside. It went about 5 hours.
When it hits 125-130F I brush it with warmed honey and sprinkle it with cracked black pepper, then leave it on another 20-30 minutes until it hits 135F.