Engine braking strength is dependent on two things. One-the clutching's back-shifting strength down to the one-way which is in the selection of springs and weights. Two- the resistance offered by the engine with closed throttle plates (TB butter flys). Sense #2 is what it is and can't be changed without damaging or effecting the engine operation, one can only effect change with the clutches...but not without the expense of effecting shift-out along with all other clutch related operations. You can go back to a lighter secondary setting but B1 is the lowest. You can put a lighter spring in the primary and/or heavier flyweights to slow the back shift..but all effects the other direction as well. For many, its has been the resistance of the throttle peddle spring that has caused the unreal jerkiness of on and off throttle. If you can lay your foot on the peddle and it goes down with just the weight of the foot, it's too light and must be increased to the point that you have to push just a little to push it down. This will smooth-out the rough trails and stop foot fatigue.
I assume you have a ZForce as you posted in the Z section but your avatar shows a CForce.