Chief wrote:
I do this all the time and have become quite the Dremel Master when it comes to modding heads for 25A.
For something simple like what you're proposing, I do the following (if you don't have the tools, then I don't know what else to suggest):
I take the rounded "gouging" bit for the Dremel (the one that's about 1/8" or so and round) and I Dremel down in short spurts. I "wobble" the tip of the bit to widen the hole, but allow for the "lip" to remain so that the neck ball will still pop into place (you might want to widen the "lip" in the socket just a tad with an Exacto rather than trying to Dremel it on your first try.) Sometimes it takes several tries to get it right - be patient and don't take out too much at one time. Try popping the head on after each quick spurt and see where you stand. The Scarlett head is only slightly tighter than the Jaye Head, so it won't take much work. If for some reason you slip up or gouge out too much from her head, you can pack some green stuff or Super Sculpey in there like Matt mentioned and try again once it's cured (but it's better to get it done with the original plastic.) But fitting a Scarlett head on a Jaye neck is a great place to start since it's the easiest mod you can make on 25A figs without it being a straight-up LBC.
Hope that helps and wasn't too convoluted an explanation.
Chief's hitting the write spot with his tutorial (maybe add it to the wiki). Just another step if you see there need is that if you have to use greenstuff or Sculpey to tighten the neckball, cover the sculpey/gs with superglue once it's fully hardened to lessen erosion.
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