As one comment mentioned, don't skimp on the ground rod.
My advice on ground rods and wiring is to not use any aluminum connectors. (not sure if they are legal)

Many problems with aluminum wiring and connector clamps. Aluminum can passivate over time. (meaning it can become nonconductive)

Once when trying to explain this to an engineer, he told me, "you can't know that." He was one of the dumbest engineers of my acquaintance. Though it does seem people with higher degrees often have difficulty dealing with 'average' problems.

jtk