You can certainly make it work depending on how much is going to be inside it. With 4" depth though the PID(s) on the face cannot have anything near them on the inside, because they're almost 4" long. Contactors are also a bit tall. It's been a few months since I built mine, but I think mine might have been close to 3" tall, so you can't have them under any buttons or switches with the 4" deep cabinet.
It's certainly a good box if you're building a budget system. But if you're building a $2,000 monster or whatever, I'd drop $80 on eBay.