Wow! I'm really impressed. Of course your dog's ability in the field has as much to do with your tenacity and expertise as it has to do with your dog. I have never gotten either of my retrievers to be good in the field (my own laziness, mostly.)
Max just doesn't have the concentration. We went through intermediate obedience (barely) and about 3 sessions of agility (he has his own small course at home) but he just wasn't enjoying it. The winters are long here, and most of the training has been indoors. He'd rather run like the wind in a field off leash. 2 different instructors goaded me into using a shocker on him (total 2 times) and I didn't like the effect at all! I decided that it just wasn't worth it. We certainly weren't going to win any prizes, and if he wasn't having fun, then why bother?
Of course I've lost 60 lbs since then, and perhaps we should try again. I could probably keep up with him now! LOL.
I suspect that his original owner used an anti bark collar on him and that is why he NEVER barks, unless he is surprised by a strange animal. Then it's just one "Woof". When my trainer shocked him because he ran right into the observers after a triple jump in a room that was too small, he refused to go over those jumps for about a month afterward.
I switched trainers and the same thing happened at the new place when he got boisterous. He then walked slooooowly through the course. I have a $275 collar that has been used twice! If he is misbehaving (when company comes sometimes -- jumping to greet, etc.) all I have to do is to put the controller on around my neck and point it at him, and he calms right down. No collar -- just threaten him with the controller!
Then I found out that if I just point my computer portable flash drive at him that I sometimes wear around my neck, I get the same effect. Instant goodness!
They say they don't know who is doing the shocking, but I don't believe it for a minute. Golden's are too "soft" for shockers, IMHO. They naturally want to please -- even the hard-headed males.
The way it was explained to me is that the collar should be used at an extremely low level, just enough to annoy, not scare or hurt. The idea is to teach the dog that obeying the command turns off the annoyance. You do this by "collar conditioning" which is a long and careful process. And you never use the collar to punish, only to reinforce a command that they already know.
We went to a high-up Retriever Guru seminar (Evan Graham) and Shelley was the guinea pig for a session of collar conditioning and teaching the command "Come!" She never yelped or jumped - the typical collar (TriTronics) has 15 settings on low, medium and high for a total of 45, and we never got her above a low "2" and settled on a high "1". I sometimes bump her up to low "2" again if she's really jazzed.
I tune her up once every couple of weeks, and she comes like a shot.
Since Max has already had bad experiences with a bark collar (which does really hurt) he may not be a good candidate for a training collar. But we do have plenty of people who use them on Goldens - but very carefully.