Extra neck frame parts too tight?

So I ordered one of the 50cm Neck Frame parts from Hobbysearch so I could stick my SmD Genesis head on one of my AP bodies. It fit well...but it turns out it fit a little too well, because when I went to take the head off today to put a different shirt on them the head was nearly impossible to get off. It was so tight on the torso frame that I ended up having to heat the whole thing with a hairdryer until I could squish the (thankfully soft) chest parts down far enough on the frame that I could reach the neck to pry it off.

I experimented with my two AP heads that came with Neck Parts already attached, and they both pop on and off just fine; and it does feel like the hole where the chest post goes into the neck is slightly bigger on them. I'm assuming it has nothing to do with one of the bodies being 50cm and one being 48cm, because I think the use the same chest/neck pieces yes?

TL;DR, why is the new neck piece I ordered as a spare so much tighter than the older neck pieces that came with these dolls, and is there any way to get the frame pieces to fit properly? @K-2?

Edited July 18, 2021 by monkeypizzasonic

There are a few reasons these interchangeable parts will seem to fit poorly. The molds for the hard plastic skeleton parts are normally made of stainless steel. These original molds are over 15 years old and expensive to replace. If these are the original molds, they can change in size over time with all the heating and cooling cycles they go through. This will cause the more recently made parts to be ever so slightly out of spec from the original parts. Likewise the brass molds used for the soft vinyl will change size over time due to this heating and cooling. There also might be a little bit of "flash" on one of the parts, which can cause the parts to bind.

Please pardon me as I may be repeating information you have already mention just to make sure we're talking about the same thing. I'm old and as someone (Kizuna) likes to point out my brain may be fossilizing. I also want to mention other issues other owners may be having with similar symptoms.

So is the neck piece hanging up on the "peg" on the top of the chest skeleton part or is the neck piece sticking in the soft vinyl of the neck/chest part like the neck area is too narrow? Or possibly both?

Try fitting the neck parts without the chest vinyl. Do other neck pieces hang up in this chest part? If just this one new neck piece is hanging up, roll up a piece of sand paper (about a 200 grit) and give it a couple of passes inside the new neck piece. Make only a couple of light passes and test fit the parts. You don't want to take too much material off and have it be too loose.

If all neck pieces hang up on the chest part, lightly sand the top of the chest part.

If it's not the hard plastic skeleton parts, do all neck pieces fit tightly in the chest vinyl? If the neck area of the soft vinyl chest part seems to be too narrow and holding on to all neck pieces, you can try sanding the exterior of the offending neck piece and /or "lubricating" the interior of the vinyl neck area with a little baby powder.

I hope this helps.

Edited July 19, 2021 by K-2

@K-2 Thanks! It's just the one neck piece being too tight on the chest skeleton part. I'll try sanding the inside a bit and see if that helps.