Thanks for the feedback Roger. The Rio is 2008 model.
I thought I was downhauling enough but after checking out the manual again and looking at some youtube videos I reckon it probably wasn't enough. Will try a bit more next time and see how it goes. I'm happy with how the leech should look but probably been in too much of a hurry to get on the water to do rig it properly.
It is the same specs as the one recommended, 460cm, IMCS 25 etc, however it was a cheap Arrows?? brand I believe. I have read that the correct mast is a big factor in the correct rigging of the sail, however wasnt sure if there was noticeable difference between brands of sail... and carbon content. My understanding is carbon content only decreases the weight - which has beneficial follow on effects.
I have "tried" the Rio with the centreboard up a couple of times so will get comfortable with that before upgrading to a Futura.
Thanks for the help.