That sounds about right Peter.. On my 8" F/6 newt that I used to have, I was about 5mm shy of getting focus with my 350D, using a mates paracorr I was able to focus with, yeah say 5mm of spare inward focus travel to play with.. Now, We have to do some sort of, Anti-Rain Dance and get some quality imaging time in over this new moon weekend!
Alex.