I`m thinking of replacing my Panasonic ptae300 with a 4805. However it would have to be mounted about 15 feet away from my 67 ins wide screen. According to the throw ratio calculator on the infocus website this would be much too far to obtain a 67 ins wide picture. Does anyone know if the lenses are interchangable on the screenplay range or can you buy a telephoto attachment? The sp5700s throw ratio is much bigger and would do the job (but I can`t afford one).