As far as the place command, it all depends on your dogs level of obedience with that command. I believe I am the one who suggested the place command to start teaching your dog how to be calm. But that was 3 days ago. You cannot teach a dog the place command and then a week or two later after practicing with either no or minimal distractions, put him in place and expect him to stay there when a stranger/guest enters your home if you have never practiced that.
You probably will have a hard time passing a test you never studied for. You cannot expect your dog to succeed in this situation he has never been in or practiced before.
You cannot wait until real life happens to show the dog what is expected of him right then and there. If you want your dog to be comfortable in place when people come over, you need to teach him that.
That means you need to take time out of your day and have a friend or two help you by pretending to come over and enter your house. You know its a training exercise so you will be prepared. Your dog won't know the difference.
As far as the hackles/barking/backing away... Regardless of the reason he is doing that (most likely scared), its an unwanted behavior and potentially dangerous behavior. You have to have a way to follow through if your dog acts this way or breaks place. What tools are you using to teach place? You have to have a way to tell the dog no.
To be honest though between the two threads you have made, it sounds like you need to keep building upon the relationship with your dog. There is a reason he is acting the way he is when guests coming over. I'm not buying the whole GSD thing, I understand these dogs are bred to be protective but this dog sounds like it is scared and doesn't feel safe, he feels he NEEDS to protect. You need to be a leader for this dog, showing him you've got his back and everything is under control. Teach him what is acceptable and what isn't. Dogs will do whatever you let them get away this.
Sage - Sable GSD - DOB: 8/20/15