Thanks for the help, but I've never used PMDs 'cause I don't trust those external binary morph stuff.

(Tried it out once, promptly lost some work, never switched it on again)

But I already solved the problem the old school way, by making a joint center injection pose with my trusted cr2 editor:

(For those interrested: Just delete the first block of the figure's cr2 file and save as a pose file. The second block will overwrite the joint centers data, but will leave the weightmaps in place)

Left the weightmapped H3 with the original H3 joint centers injected back, right the weightmapped H3 as derived from my weightmapped Aiko 3.

Clothes are standard non-weightmapped Hiro 3 clothing straight out of the box.

The weightmapping causes a bit of cloth pokethrough in extreme poses, but that is to be expected and could be easily fixed.

I'll refine the weightmap a bit and transfer it then over to the original Hiro 3 geometry file. (I suspect H3 and A3 have slightly different mapping)

Then I'll see how well this works with one of my custom sculpts.  :-)