Welcome aboard Kev!
I also have the CharGriller and yes, it does need a few mods right out of the box, one of which you are already doing... the chimney mod.
The CG is notorious for that hot spot at the firebox end. If you are gonna use it strictly as a smoker and not a charcoal grill, then install a permanent baffle at the opening into the chamber. If not, you can flip the charcoal tray upside down and hang it above the top of the opening... that serves the purpose pretty well.
Also, DO NOT depend on the stock temp guage... it isn't worth the hole it mounts in! Get yourself a grill surface temp guage, or an oven temp guage, they're not expensive. Or, for around $40, you can get a Maverick ET-73 remote digital that has dual probes - one for the food and one for the chamber grate temp. You can also install a quality guage (or two) in the lid at grate level. I installed one at each end of my lid to monitor temps from end to end.
So, there you have it. You have a great piece of equipment, and with a few mods, you'll have an even nicer one! Good luck!