As there are a few ways to strike with the Tonfa, may I ask how you are striking?
1) Holding the longer tonfa shaft and using the Short Handle that is perpendicular to the shaft as the point of impact?
2) Holding the longer tonfa shaft and using the opposite end (the grip/handle) as the point of impact?
3) Holding the tonfa by the Short handle that is perpendicular to the shaft and 'spinning' it to strike with the end of the long tonfa shaft?
Sorry I thought the way I described it would be decently clear. I am holding the short handle perpendicular to the shaft and spinning it to strike with the long end of the shaft. Any other way of holding it would cause the same amount of force to transfer back as if you were using just a normal expandable baton.