I have a 9.5 inch Gold Dot Dagor in an Ilex that I'm running on an Ansco 5x7. I'm told it will cover an 8x10 OK (does this sound right?). I'm looking for either a good 21" Dagor (will this cover an 8x10 when I upgrade?) or some or other triple convertable lens. Can I get by with a barrel shutter? And just what is a barrel shutter? How good are these convertable lenses, and are they at all easy to come by? (I've been haphazardly looking for a 21" for a couple of years; I've never come across one in Toronto (I live near there), I came across a 19" in Chicago, I expect I'll have to go to New York to get the 21". Any suggestions? I had read somewhere that Andreas Fenninger built himself a really long lens -- have you ever come across any literature on this subject?