Preheat oven to 250F. Place rack in middle of oven.
Pulse-grind bread in food processor to form soft crumbs. Place rack in middle of oven. Scatter crumbs on baking sheet and toast 15 minutes, until light golden. Raise oven temperature to 450F.
Let the crumbs cool in a bowl and melt the butter. Toss crumbs with butter, hot sauce, chili powder, smoked paprika, garlic powder and cheeses.
Cover the cooled baking sheet with parchment paper. Trim a thin slice off the bottom of each potato, giving it stability. Trim the ends then thinly slice the potato across but not all the way through the potato -- stop 1/4 of an inch shy of all the way through. Slices should be 1/8 of an inch thick but no more than 1/4 inch.
Gently fan out the potato slices and rinse off the starchy juice. Turn potatoes cut side down on a microwave-safe dish and cook on high 10 minutes. Let cool enough to handle, about 5 minutes, then set the potatoes cut-side up on baking sheet, leaving lots of room around each potato. Coat with liberal drizzles of EVOO and season with salt and pepper.
Roast potatoes 30 minutes then remove from oven and gently stuff the chili-cheese mixture in the ridges of the potatoes. Turn on broiler and broil potatoes in the middle of the oven until deeply brown and bubbly, 3-5 minutes.