Thank you very much for your kind reply, C. Alexis.
I just downloaded Portable MusicBee a day or two ago, and it is version 1.4.4. So I figured we were still on v1. After your response, I looked at the downloads page, and I see that the installed (registered) versions is now 2.0. I hadn't noticed! I'll have to update my installed version to 2.0. I wonder if the portable version is also at 2.0. I'll have to download again and find out.
Hopefully, those two nice skins will work in 2.0, as you suggested.
Can I infer that any skin with the xmlc extension will only work in 2.0?
Again, thanks for the help.