A little over heating isn't going to hurt. I don't know which end when you say the top, if you are holding the jig by the hook do you mean the collar portion or the head? Is it the first part that hits the paint or the last? If the collar isn't getting fully painted then it is a heat issue, try a few more seconds of heat and don't worry if you get a little smoke. If the paint doesn't scorch or bubble you are fine, over heating becomes more of a problem when dipping in a jar because you end up getting too much paint on the head and when you cure it the paint will sag and you get the dreaded "nipple" hanging down. In a fluid bed a little over heating works fine and ensures you get full coverage, I've been doing this a long time and when I discovered powder paint in 2003 it changed the way I do things. That said, 15 years of using it and I still will have certain type heads that end up with a puff of smoke after I paint but they come out flawless. So don't worry about adding a little more heat, like I said, as long as you don't heat to the point of the paint scorching you'll be fine.