If it were me, I would mount it on the carriage right in front of the round white bar you are holding in one of the pictures. Then I would get someone to rig it so that you could have a handle to squeeze on that white bar, or something that would turn it on and leave it on at the speed you need to go. That way, the control is always where you need it in relation to the machine, you are not tripping over it, and it is easy to reach if you need to turn if off quickly. some kind of a lever action thing ought to work out.