So I was all wired up this past friday night, and because of my goof I shorted 5 of the 8 FETS (I think), so I've ordered up some replacements. I moved the board down to the back of the playfield, thinking that typically the playfield is going to be tilted up (which means the back will be the lowest point). Even with 6 of 8 solenoids wired up, you can see that now that I've got some wire management, it's still very clean underneath (it will fill up later once switches and lighting is installed).
I've written on the playfield which connection is which with abbreviations. I should probably label each faston as well so I'm not guessing what goes where if I need to unplug the board.
While the extra channels were working, I got to see how one of the slings and the ball trough worked. The sling is certainly overpowering (it launched the ball nearly all the way up the playfield), and the ball trough solenoid kicked the ball so hard it almost bounced back into the trough. The slings can be turned down later with code, and the ball trough can be softened by adding a gate to slow the ball down a bit.