Some of you on here have probably read several posts where I ask very novice questions due to lack of experience with a GSP. Here is another!

My GSP (Maverick) is now just over 1 yr old. He's a great dog, obedient most of the time when he decides not to be stubborn and a blast to do anything with. My one "issue" is that I feel he is not as friendly around strangers and is a bit on edge it seems a lot of the time. He wasn't socialized alot as a young pup and we take him everywhere but he just doesn't easily warm up to most people. We had one friend over, and after barking at her initially, he eventually warmed up to her and was laying with her on the couch napping. Most of the time though he will go up and sniff them out and for some people, he will allow them to pet him but only under the chin. Anyone going over his head he either barks and sometimes lunges or just jumps back quickly. I know that is a dominance thing so I understand somewhat why he does it.
This weekend we had quite a few guests over (roughly 20 people) and while he did ok, at times he definitely was stressed and had some people uncomfortable because although I know he is harmless, when a 50 lb dog barks and is lunging at you, it can be intimidating. It happens more when people get closer to his face but he will also do it to random people just sometimes reaching for something near him. My question is, is this sometimes normal GSP behavior and should I be concerned it can turn into fear aggression? I should have put him away as I am sure putting him in that position was not doing him any favors. I don't know if it's a behavior in response to feeling the need to protect his territory or he just doesn't trust strangers yet at all. Or at least in settings where there are too many people. I hope he can get to the point where he just wants to play with everyone like he does with us, but will accept if he never gets to that point. I know he is still young but still something concerning to me at least.