Ordered the NPT plugs needed to finish the case. Reviewing the sizes given in the blog and my (partially NPT plugged) case, I need the following to complete the job:
3x 6mm plug = 1/16 NPT
2x 8mm plug = 1/8 NPT
0x 10mm plug = 1/4 NPT
0x 12mm plug = 3/8 NPT
https://bobhooversblog.blogspot.com/2007/06/help-more-on-plugs.html