I started with a new image in .pspimage format with a trans background & created a new taskbar using native trans in a portion of the image. I saved it as a .png using the optimizer, selecting alpha channel trans & existing transparency. I then let SKS5 import the image & convert it to a .tga. After saving the skin, getting rid of the skin cache files & rebuilding the skin list, then applying the skin, WBConfig previews the Taskbar correctly but the actual Taskbar has no trans:

I double-checked the code settings: Trans=1, PerPixel=1, AlphaMode=0.
It appears that PSP8 saves the .png as a merged image & still strips the trans somehow, despite WBConfig's Preview, as when I open the .png, it looks different than the source .pspimage:

I feel a little like Alice, as in Wonderland.
Any additional ideas?