Well, since I titled this thread as a "worklog" I guess I had better treat it as such and post my progress.
Little tact switches under the dpad, big ones under the buttons. Works well.
Purple and black look great together, in my opinion. The crud on the dpad will be cleaned off with some rubbing alcohol before final installation.
Drilling/filing that dpad hole was a pain. Luckily the two button holes to the right of it (not pictured) were WAY easier and faster.
Lots of extra space with the perf board so I can mount it nice and sturdy. I might even use standoffs instead of just hot glue to hold the controls in place. Imagine that!
If you watched the YouTube video, I mentioned that I'm using a GameCube power switch. To turn the unit on, you'll need to push this grey button down...
and it will depress into the case like this. Trust me, it will be cool.
No, I'm not leaving the perf board on the outside of the case. I was just testing the layout of the buttons. Everyone does that.