Watch out for METALOADSKN ... when you use it, FIRST take a backup of your current System Key Numbers with METADUMPSKN - or else you could lose everything! The process of loading that METALOADSKN appears to use is to first dump all of the system code's key numbers that you're loading. Then, it loads whatever is in your load file. If you don't have all of your current system key numbers in your load file, you'll lose whatever isn't in there.

I was testing. Dumped all GL key numbers:
$ metadumpskn [productline] GL
This created file GL.skn .
Copied it to a backup:
$ cp GL.skn GL1.skn
Edited GL.skn down to 2 entries (have to do it in 2 places, because there are 2 sets of table data in the file)
$ lx GL.skn
Then tried loading:
$ metaloadskn [productline] GL.skn
Checked what happened:
$ skndef [productline] GL
:lala: Aaaagh! Only 2 entries !!
Restored all entries:
$ metaloadskn [productline] GL1.skn
Checked again:
$ skndef [productline] GL
Okay :disco: they're all there! Whew!!