In principle a Go Joe works. The problem is that users of it don't learn to bodydrag upwind. They will then encounter a problem when the Go Joe implodes or they are testing a board without a Go Joe. I will recommend taking small tacks when in waves in order not to get too far away from the board.Go Joe implodes
well you are more lickly to have your kite blader implodes thant your GoJoe (assuming that you do not pump it like creasy.testing a board without a Go Joe.
I guess that 99% of the kitesurfer kite with their own boards and never test other boards.