If you have to slow the injection speed down to prevent overshooting or gas entrapment during injection; then you are probably filling the mold too much during first stage fill.
Comment: We can use one speed to fill most of the mold, but we always have to slow the screw down as it gets to the the end of fill to prevent flash and gas entrapment.
My Response: The best approach to complete the filling of the mold is to transfer to pressure-controlled packing and let the screw slow down as the mold fills and the pressure builds in the cavity. Actually, the point where you start your slowdown is likely to be a good transfer position.
Additional Thoughts: Keep in mind, you should transfer from fill to pack at the position where the mold cavity is 90-95% fill. This is based on the mold cavity being 100% full with 1st stage only (when the first cavity fills if multi-cavity).