Pistol Port Location?

[scouttech]

I'm doing my first 300 Whisper project. I've seen where you guys are saying the pistol location is the better spot to put the port.
I've found the port size but can't find a call out from the end barrel or extension.
Please help, 12" barrel.
I've also looked in Brownell's and Midway for a pistol gas tube, where do you find them? Or are you just making them?

Thanks,
Tom