Bird box with clear roof

One of my boxes which has been used two years in a row now was always quite dark inside been on the brightest of days so this year I decided to put two windows in the roof it is a pitched roof type. Ten I covered it with perspex, it has greatly improved the quality of the images and so far the bird dont seem fussed at all. But they only holes about an inch or so round I am not sure about a fully clear roof, if a predator sees inside it may put them off, but anyway good luck.