Did you run a thermo in the meat?
That's the big trick, time/temperature is a good guideline, but it's never always the truth. I had a 17 pounder finish up within 12 hours, while I was expect close to 25 - had I rolled over and kept it going the other eight, then I would have been serving pizza come dinnertime.
The other thing I never do anymore is trim down the whole packer, I leave the fat as-is, fat down toward the coals in my WSMC as an extra thermal buffer. Whatever doesn't render off or become bark gets trimmed on the board prior to service.
I also agree Adiochiro - a water pan is a must. I actually switched over to what I call a "mud pan" where the water pan is filled with play sand to keep the heat sink action steady, but I wet it with water to add moisture to the smoke. Wetter smoke environment actually makes a big difference for the end product.
Foiling is optional, but it's the best place to begin, I never foil, keep the smoker at about 215, and trust my stock thermometer less than I trust a frayed rope.
Hope this helps, and good luck with your next round of smoke!