Besides the basics of wire gauge/current/placement and fuse size what subtle things did you find that you felt were necessary?
1) Label it, label it, label it. If yours in being inspected, buy yourself a nice $20 label applicator and label everything. Do it to the point of even being silly and obvious what the damn thing is... like "Charge Controller Monitor", "DC disconnect", "15A AC Breaker", "DC grounding bus", even the wire gauge and type ("8 AWG USE-2"), etc. My inspector commented that I obviously knew what I was doing (not so sure of that myself LOL!) and that it was labeled so nicely, anyone could follow it. So, take the extra time to wire it up neatly (all wires horizontal and vertical) and label everything. Post a laminated wiring diagram on your board even if it is hand drawn like mine was.
2) Go bigger on wire sizes whenever possible. I didn't want him to get out his calculator to determine if I needed to be 10 gauge or not on the combined DC wire.. so I bought 8 gauge.
3) My inspector was MORE INTERESTED in grounding than anything else. (After all, that is the main safety feature). I had to explain to him that I ran the 6 gauge bare copper ground wire in one solid piece, to my frame on the roof and attached them twice to each panel via WEEBS with grounding lugs... then run down and thru the isolator box and over to the main boards where all the boxes were tied to the grounding bus and then to the 2 8-ft grounding rods pounded into the ground 10 feet apart. He spend as much time looking at the grounding as he did the rest of the time checking everything else. He was not there 20 minutes. He got a "sense" that I knew what I was doing and just checked the critical stuff.
4) Customize your system LATER, after the inspection. Not saying to do anything out of code, but if you want to run a whole circuit to your pond pump underground, just run it to a circuit and a gang box.. and do the underground to the pond pump later and down the road. 2 reasons... 1) you'll get bogged down and never get it all done to be able to get it inspected (I had a 6 month time limit) and 2) it complicates their job by another factor.
5) Don't hesitate to re-do something if you later discover that you did it wrong. For example, I used leftover 20A GFCI duplex receptacles in one of my new 15A post-inverter circuits. Wire was 14/2 which is right for 15A, circuit breaker was rated for 15A but then it dawned on me that on weekend before my inspector was to show up for the inspection, that you aren't allowed to have a 20A receptacle in a 15A rated circuit. Why didn't I notice that before?? I'm such an idiot! So, I ran to Lowes and bought a 15A GFCI and redid it. I knew that if the inspector walked in and saw that first thing, he would question everything else more closely. Another example: Load versus Line for DC breaker box -- for panels versus charge controller was opposite what I initially thought made sense.. I probably rewired 5 different things like that that I didn't think thru very well the first time.
GOOD LUCK!