I fit both if I can. The fans are loads quicker than pencils on large windows or as said, windows that bead. Yep, you do have to make sure the frames are cleaned as well.
There is room on the brush for both types of jet. Put the fans outside the pencils and have two y pieces etc. So just leave the fans in U.S bloke, they do come in handy. Drill some holes and put some pencil in as well. The weight is negligable. They do come in handy sometimes although you won't use them as much. (That's about your other post about taking them out).