Simple
John, I don't normally skulk in this group, but I can't believe no one answered you. Were you referring to a fixed ring for the pole? If so, it should be where it is comfortable for you. I asked the same question and got no answers. I put mine about eye level for me so it would be easier for me. I also added a topping life to support the pole when poling out the jib and led it aft through a spare block.
FWIW, I went with the Forespar ring. I really liked the look of the Ronstan one at West Marine as it is a tank, but it looked so beefy that I was afraid I would not be able to get it to conform to my mast. Put the Forspar in a vice, squeezed it a little and it fit/conformed great.
The best way to go would be to install a track so you could move the pole up and down. That is what I wanted to do, but on my 310 it appears they have a wiring track running right up the front so the fixed ring straddles that. Ray