OK I am a wannabe engineer so here is my story. I am a long time rider. My wife only rides tandem and never rode before. She has a bike computer on stoker bar and would slack off as we approached our target speed. I put a piece of black electric tape over the speed and asked her to focus on her heart rate. Not wanting to force anything on her I did not set a target. When I feel my work load getting higher I kindly ask her what her heart rate is. When she heasitates I have a clue that the number is real close to what she sees on the screen
. Problem solved! FYI using CatEye V2 wireless, one sending unit with two head units.