Basic question on brake lines

[focusedontheprize]

After I get the parking brake assembled this weekend, I am going to be able to start running the brake line. This is my first time doing this so I have a few questions:

1949 Chevy truck
Front brakes: Classic Performance Part's 5 lug 4 3/4 disc conversion
Rear brakes: 1997 Ford Explorer 8.8 axle and OEM brakes

Brake booster is apart of CPP's 5 lug conversion.

I called CPP yesterday and was told they run a 3/8 fitting on the proportioning value for the front brakes (for both sides, 2 separate lines to each front corner) and a 9/16 fitting for the rear brakes.

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With that being said I am running 3/16 line, so I was told inside of running adapters to size down to 3/16 line, I could just put a 9/16 flair nut on the 3/16 line (again I am flaring my own lines) and that would clean everything up. I would could do the same for the 3/8 fittings in the front brakes.

So my question is, would this work? I assumed as the size increased (to 9/16), the hole in the flair nut would also get larger so it would be bigger than the 3/16 line.

Any help would be a huge help. Thanks.