First off, welcome to the Do-It forums.
Next the help. Look at the picture I've included and using a shop knife with a NEW blade in it, and a steel straight edge, scribe lines in the metal where the pen marks are. You DON'T need to cut between the top two sets of bodies where the pen mark runs to the runner. You want the cuts thru the bodies in the first full ring ahead of the tail section. Next be certain you tail pieces are cut at or slightly behind [toward the tail] that ring of the body. When making your cuts in the metal use a fair amount of downward pressure but be careful to not let the knife slip into the body cavities if possible. Also, do a trial shoot with the mold clamped up tightly with a single color to see if flashing is present. If I is, simple open the mold on a flat surface and run a fine flat file across the face you've cut...very lightly! Only a sweep or two of the file will knock down any ridging that occurred with the cuts. Do another trial shoot and you should see good clean baits.
Now when you trim the tails from the tail mold make certain each is trimmed so that their cut face is slightly behind that new vent line. My 2" flapjack mold shown doesn't deal me any fits so its not been vented but I have molds that will act up if not vented thusly and they like to be filled slightly slower and with slighter warmer plastic.