I have ths happen with 1/16oz shaky heads and like cadman said and you already know, powder paint will stiffen them up until it chips. I agree with smallmouthaholic that on spinnerbaits and buzzbaits that if it is loose there isn't a lot you can do other than repouring it. I disagree with smallmouthaholic when it comes to leaving it in the mold, it WILL help, I'm not talking 5 more seconds, I'm saying if you pour the head and pour so the sprue comes over the top of the mold and then leave it sit for 15 seconds and then open the mold and take the head out by the spru that it will bo on really good. Another trick you can use is epoxy, I like to epoxy coat my painted shaky heads, and even though they are on the hook pretty good I stil worry so after I'm finished coating them and my epoxy begins to get stiff, I'll take a little of it on my brush and add a small amount of it at the base of the head where it meets the hook. That will hold the head in place for a long time.