Preheat the oven to 375 degrees. Place the potatoes on a baking sheet and bake for 30 to 35 minutes, or until the potatoes are tender and the skins are slightly crisp.
On a cutting board, cut off the very end pieces of each potato, then slice the potato into 3 to 4 equal slices. Lay the slices flat and use a round cutter or a spoon to remove most of the insides. Leave a very thin rim of potato around the edge for structure. As you go, dump the insides into a mixing bowl with the butter and sour cream.
Add milk and mix the potato mixture together until smooth. Add bacon, salt, pepper, seasoned salt, and cheese, and mix together. Taste and make sure the mixture is seasoned adequately.
Use a scoop or spoon to fill the potato slices with the potato mixture. Slightly mound the mixture in the slices, as it will settle after baking. Top with additional cheese if desired, and bake at 375 for 8 minutes, or until the cheese is melted. Turn on the broiler and broil for 3 to 4 minutes, watching very carefully so you won't burn them.
Remove from oven and let sit on the baking sheet for at least 10 minutes before removing with a spatula and serving. (Note: Filling will be soft, so the longer they sit after baking, the easier they'll be to remove.).
Can make these well in advance and keep in the fridge or freezer, unbaked!