When you let go of him and the field, does he just take off never to return again or does he just take a big first cast and then settle back?

There are things that you can do to keep him close, but I have found that it is better just to let the dog hunt in the range he is comfortable with. Otherwise, you are going to have to stay on him constantly to keep him in your range rather than allowing him to comfortably work in his range.

If he's a big ranging dog and you're hunting tight cover, you might consider getting a Garmin Astro. Takes the risk of losing the dog out of the scenario.