1) If you are building a "Woody" type enclosure, Walnut wood is TOUGH - especially 1.5" of it. Consider using a Dremel saw to cut it (I bought one specifically for this project). A hand held dremel/saw won't cut it (excuse the pun).
2) Wiring - given the tight working conditions wire the relay board BEFORE you attach it to the back panel.
3) After plugging it in - give it a full minute to warm up - it takes a little time to start up - which can be scary when your starting it up the first time.
4) Remember to plan your air flow, because of the way I cut the back panel to accommodate input/outputs - I have plenty of air flow.
I'll post some pics as soon as I can - I'm travelling so it will be the end of the week.