Thank you.

Linear interpolation ? Yeah, that fits. And I've done the origin/parent thing with eg a tool-box. Though I may not need demo, please, please, post it !!

This box is a single object, but I can 'fork' original, editing it to stand-alone tub & lid OBJs. Still, I'm a bit sad, as it means I must be very wary of other MMD/PMX morphs.

From what you say, 'linear' morphs should be okay. So eg a panel-van's sliding door should be okay, while its hinged cab doors may be okay-ish with a modest angle of eg ~45º. But its big tail-gate doors, which swing ~270º, must be 'Poserized' as you describe...

Again, thank you.