For sizing of the Dominant Dog Collar, should the collar measurement of the neck go into his recess rather than over it?

Dear Cindy,

I have a 4-year-old male Dobermann who was 3 when we got him. He had not been well cared for, but is fine now after a year's work, and is up to a good Dobermann weight of 42 kg. He responds fairly well, but is quite difficult on the lead --- and elsewhere sometimes. So I thought a Dominant collar rather than a prong would be good start to serious training effort. Re sizing: as you run your hands up the back of the neck to the ears, there is an indentation just behind the ears where the bone structure changes. Should the collar measurement of the neck go into this recess rather than over it? I should be grateful for your help.

Sincerely,
Mark