Your specs have really boxed you into a 16-35 f/2.8L in the Canon product line. As you probably know, that’s a $1,400 lens. With the 5D II running at around $2,000, might this be the time to jump to FF? 17mm on your 40D is equivalent to 27 on FF, so your 24-105 would actually be wider than what you’ve been shooting with.