haha!! welcome to owning a boxer...i had the same problem with Reese. supposedly they grow out of it, but Reese still tries to get into the cat box to eat that poo. She stopped eating her own poo a while back, but every now and then i will catch her when she is outside trying to grab a snack. I say loudly and firmly "REESE NO...DROP IT" - and she usually drops it....but in the case that she doesnt i clap my hands and she drops it. I have got to the point that i leash them every time we go out....since i did this no poo eating incidents. Make sure you keep a really close eye on him so you can catch him
Didn't see this in the article, but meat tenderizer can be added to his food to stop him from eating his own poop. Pineapple is supposed to work, too. I would guess papaya would, too since meat tenderizer is made from pineapple and/or papaya extracts.
Hanna did this a little while back and I used the spinach or pineapple method. She never did it again. There are a lot of other supplements you can add, but I prefer the natural way, and it worked - good luck!