If You're getting "hollow heads", that's because the cooling plastic is drawing up, needing to be "fed" more liquid plastic as it cools and shrinks. I always...always...hold injector pressure for 8-10+ seconds after the cavities are full...then twist the injector about 1/4-1/2-turn to break the cooled plastic between the tip of the injector and the mold sprue, then fill up the sprue with more plastic as soon as possible as You draw the injector from the sprue.
I always filled my sprue after the cavities were full, but still sometimes got "dents" along the sides, and sometimes hollow heads/bodies. All of this is from not feeding enough plastic to the mold, to supply the needed plastic to the cavities as the plastic cools and shrinks. Once I started holding injector pressure, almost 100% of these issues went away. Sometimes I'll try to get fast (as if I don't have enough time to do it right), and I'll start to see the "dents" on some baits again. Hold injector pressure (light pressure...hand-weight) for about 10 seconds after it's full...then top-off the sprue. Your consistency should greatly increase...meaning the quality/frequency of "perfect" baits.
If You've ever gotten the little dents in the Tails of the Gliders...holding injector pressure seriously reduces those dents, as well...at any shootable temp.
Edit: The 4" Skinnies that are curing as we speak, were all made holding Injector Pressure...they are as perfect as the mold cavities...every one I shot is like that. They're actually a pleasure to look at...truly a Premium Custom Bait.
