Which swift box designs are most successful?

  1. For next year's swift season I want to install a few swift boxes on the gable end ( sloping eaves) of my property. It  is south facing but is sheltered somewhat by the roof. However I am getting a bit confused on which design of swift box to use (there are so many). Due to the sloping eaves the box won't be able to be tucked under the eaves like a flat eave would so it would either be mounted directly on the wall or as close as possible to the eaves. Does anyone have an idea on the best design for my situation and box that would be most successful in attracting swifts. Many thanks.