i did some windows at about 40 foot with a wagtail but it was just too high to get fine control ,i was using the biggest wag i had ,a 24inch to reduce the effort , in hindsight id have got better results using the method i wrote above . also at that height you really need 2 people each with a pole ,one to mop and 1 to squeegee because putting up n down the pole to change over to squeegee is a drag .