...After accidentally using very nearly the worst glue I could have possibly chosen for the project (accidentally picked up the tube that contained acetone as a solvent... rookie error duh!!!), I've managed to semi-melt a 1/6 neck plug, and rubberize (yes rubberize) two old style Sideshow head sculpts. (As well as give a brilliant glassy perfectly smooth surface to the inside of one of the two heads, since acetone fumes do that to plastic...)
The heads have been left to dry out for a day, and no difference despite the stench of acetone having long since dissipated. Methinks this change is permanent...
Fortunately whatever plastic the heads are made from the sculpts themselves are still solid and stable, but damn the plastic around the necks really has gone a tad squishy for lack of a better term.
Still as a result of that I've decided "sod it" and I'm going to strip the frankly subpar paint jobs completely and attempt to repaint them.
Turns out that underneath the appalling "flesh tone" paint Sideshow used to use the plastic itself is a fairly decent match to the colour Hot Toys use for their caucasian headsculpts.
Now to determine exactly what solvent to risk, and how hard to scrub. I suspect from the horrifying thickness of the paint layers (visibly ~0.5mm worth) that an awful lot of hidden sculpt detail is going to reveal itself as a result of this accident/experiment.
(Gods though I dread having to repaint the eyes... I was always terrible at that on the 1/6 obitsu heads, though hopefully the fact that the eyes are actually sculpted in will help since the obitsus were always blank flatness!)