Downrail and uprail terminolgy can be misleading

Discussion of downrails nearly always winds up focusing on the part of the rail below the turn, and usually does so without any reference to the actual radius of the rail below the turn. Focusing on the lower part of the rail is to be expected of course because the part of the rail below the turn is what does most of the work, but in reality the radius is not entirely dependent upon whether or not the rail is 'down' 'up' or 50/50.Thus statements like " Downrails are faster than 50/50 rails is meaningless unless surfboard thickness is taken into account.Here's a drawing which illustrates what I mean: