I highly recommend Federico's place. Cute place with three private rooms and two baths. Perfect for 5.
Federico let us store our bags with an early check-in while they finished cleaning so we could walk around Florence. It was great and very kind of him to allow us to do this. He had a colleague provide us keys and take the passport photos required for stays which went smoothly at this early time too.
The only thing we thought to add for people is that the elevator is old (not something Federico can help with since it's a building amenity and not something I can rate) but if you're not into old elevators be perpared to take the stairs to the penthouse.