Side reins on a halter (a cavesson is just a glorified halter) do nothing to teach the horse about self carriage or contact. You need to think about what you want to achieve with the lunging - are you lunging for exercise? To develop connection? To develop muscles? No reason I can think of would be helped by using side reins directly on a cavesson, and in fact some of them would be directly hampered. I lunge with side reins, and I use a cavesson - over top of a bridle. The side reins connect to the bit, and the lunge to the cavesson.
Originally Posted by equitate
There are three rings on a caveson, the middle is for the lunge line, and the side ones are for the s.r. The height of the sr should be a straight line from the mouth to roughly the point of the hip (or where the rider's knee might be). Usually the inside rein is a hole or two shorter to have a slightly lateral flexion alignment.
Otherwise are you talking about how to lunge, or ????
Re the underlined - as far as I am aware, this is not "usually" the case, and is in fact incorrect. Both reins should be of even length.