Thoroughly scrub the potatoes and poke a few holes in them to vent. Wrap in aluminum foil and place on the grill over direct heat to cook for 20 minutes.
In the meantime, mix 1 ½ cups (150g) of cheddar cheese, the cream cheese, and green onions in a medium bowl until well-combined. Set aside.
Remove the potatoes from the grill and let them rest until they are cool enough to handle. Unwrap each potato and cut off the ends so they can stand up. Using a melon baller or a spoon, carve out the center of each potato, being careful not to make the walls too thin, and to leave a bit of thickness at the bottom as well. Fill the potatoes with the cheese mixture and wrap 2 slices of bacon around each one. Secure the bacon with toothpicks, if necessary.
Reduce the grill temperature to about 350˚F (175˚C) and place the potatoes on the grill over indirect heat for 30 minutes with the lid closed.
After 30 minutes, top the potatoes with the remaining cheddar cheese and cook for another 15 minutes. Before serving, garnish with a dollop of sour cream and some green onions.