Thanks! I was unsure about how the strap fitted at the back - ie over or behind the bit - I thought it went over but I didn't want to put it on and ride incase it was wrong!
5.7FB+16.2FC I got mine from Barnstormers but I think it may be a little small.
if you run your hand down the horse's nose, you'll feel where the nose bone ends and it becomes cartilage : http://www.oum.ox.ac.uk/thezone/anim...es/teeth01.jpg
you see the little spikey bit at the end - where the gap is between that and the rest of the skull - 2 on this second illustration - http://www.bitlessbridle.co.uk/images/fitting-skull.jpg . lower than that and it'll b uncomfortable - you want it on the bone, not on the soft tissue.