OK Mike here goes.
The Upper Potomac is everything were there is no tidal effect well above Key bridge. Everything thing else is the lower Potomac tidal waters. The area were you want to hunt is the lower potomac. Just remember the Potomac River is all in the state of Maryland to the low water mark on the Virginia side in tidal water and you have to have a Maryland hunting license and duck stamp. Also remember that Virginia has blind laws on alot of the creeks that feed the potomac. so be carefull were you hunt and read the blind laws if you can figure them out. Also anything above WW Birdge is DC. DO NOY HUNT THERE.
As for boat size I would not go out with less than an 18 footer it can get bad out there with just a little breeze. I know I used to fish that stretch all the time with a 20 ft Nitro and made a submarine out of it down by MT Vernon one year when the river had 5 and 6 ft swells. Read all the laws in maryland and virginia before going out there because some areas of the river like around ww bridge and hunting creek you CANNOT HUNT.
Not trying to put a damper on your hunt just be careful on that river and read the laws because MD DNR patrols that river heavily during the seasons.
I am sure there are those that will have a lot to dispute about this post.