Small update:
I got the rear panel installation finished yesterday and I'm pretty happy with how it came out all things considered. I mortised the hinges trying to get a tight fit and I did even though there is still a slight gap... but after thinking about it, the gap is unavoidable. Now of course I'm worried that the paint job will add a layer of thickness that will screw things up. This is how my stupid brain works.
I used my router to make the cuts and a chisel to clean things up to the edges to get a clean line. Chiseling MDF is not fun. I also don't have a vice and I had to clamp the panels to the side of my work bench. Even still the router wasn't perfect because at the edges there wasn't anything to support the router base so the cuts got a little wonky. It's all good in the end though.
I laid the hinges out to line up exactly with the volume knob and power socket on the lower panel. Just thought it would look nice.
Once I figured out where I wanted them to go, I used the hinges to actually draw the pencil lines.
Here's where you can see the routed out edges. Not my neatest job but nothing you will see on the finished product. You can also see the clamping nightmare I'm dealing with just to set this up. Getting the 2 panels flush and clamped to the edge of my work bench took WAY longer than it should have taken. A third arm would have come in handy...
And here's a close up so you can see the true ugliness of this effort. I was sweating more than I should have been in the 95 degree heat because I thought I ruined the panels and redoing it all was going to set me back a week.
I put it all together, including the cabinet lock, to see how it would look and it's not 1/2 bad! Nice placement on the hinges and barely any gap! Once this is painted black no one will notice (I hope) and also it's the back of the cab so um... yeah. Don't look back there!
With the rear panel open, there is plenty of room to get in there if I have to. I need to figure out a "stop" for the door though. The lock allows the door to be pulled out about 1/8" and not sit flush. I bought a magnet so I'll probably install that in the top left or right corner of the door panel so the door can catch onto something.
Apologies for the potato quality pics. I took them quickly because the dog started eating my daughter's new sandals and there was yelling involved so I got distracted. I'll try to take some more pics tonight.