Hi Pietro, both work, I would actually use the US boxes, as this opens up a huge range of use - we wanted to make the boards (and long term we will) with US boxes only, as this makes by far the most sense, to be able to move the different types of foils around/get the foil further forward than the Tuttle box position. Also from a strength point of view, way better. Plus you don't need to buy the Tuttle adaptor then! :-)