>>10134739See that ring within sonic's shoe? just don't dig/drill into that, i use that brown sand bit or those non-drill rough-sided bits so it can just focus on the sides, because that's the security for the ball socket. or just use what you have, like an xacto knife. Also the head in any case will always be a problem, because that's just how he's designed. But the this mod still helps just a bit because Jakks figured out it needed balljoints decades later.
I once even added hobby base joints to the old 5" Jazwares Modern Sonic, and even though he posed a lot better, the head was STILL an issue. BUT I never tried drilling holes or sanding out areas to make the head lighter, since there wasn't much space I could mod to hide it. Look into that.