Tuning plates would be great, but since its your first smoker that's a lot of work. Start with just a heat deflector where the heat enters the smoking chamber. It can be as simple as a throw away tin pan cut up just to keep the fire end from getting to hot. I hope that makes sense, I had pretty much the exact smoker as my first smoker years ago and that helped me a lot.
Dick's BBQ KCBS/CBJ
Custom built 6 rack rotisserie stick burner
Custom built pellet burn insulated vertical
Custom built charcoal gravity feed vertical
Weber 22" WSM