Pretty sure you could jury rig something to help indicate it, eg on park ts-2 you could lower the arm the hold the indicators below the rim so that the top of the rim will hit them at the high point only. Also if rim tape is off look for excessively tightened spokes visually (ie protruding out top of nipple) or feel the tension. If you're competent at truing side to side you could also loosen everything and start over. I guess it also depend on the wheel's value, and whether you have the time and inclination to develop this skill yourself.