I am constructing a small layout in a garage and have installed track across the back and now want to make a twin track 90 degree turn to go down the side .I would like to have the shallowest curve for best running experience and looking at the track diagram on the Hornby website I am confused as to which radius to go for, is the fourth radius the one to go for ? The shelf for the new extention needs to be as small as possible for space reasons, I am thinking about 300mm wide. Any advice before I start buying track would be much appreciated. Thank you