The difference between 6 and 7 feet is not much. A male Pokigron Suriname would be just fine for you. Most recommend feeding them mice through the first year to avoid any regurgitation issues.
If you go to the Cutting Edge Herp website, you can read up on locality BCs. Vin Russo explain size pretty well, and there are some options there to check out. Belem, Brazil BCC is another "true red tail" to look at.