He is a beauty. Wish I could help, I too have the same problem (has gotten much better) with Otis who is 14mos old. I'd be interested in what your trainer has to say once you start.
One thing that will stop Otis in his tracks is when my husband growls at him. I mean a low doggy growl, he stops and becomes submissive on the spot and then kisses and licks Daddy.
The other thing our "puppy" trainer told us is everytime he does that behavior, tell him no - put him on is leash and put the leash around a door knob so he has to stay right there, when he calms down let him off and if it happens again back to the leash....
Good luck and please share any tips you may get.