Darlene, got pictures?? I don't know what a 'drain threaded insert' is.

And what size, specifically, are the plbg parts??

I found your posting over on the plumbing forum and posted a response there.

@ci_lantro care to share the information with the rest of us that may have the same question?

Scott you will get more responses by posting your question in a new post with pictures and tag design dilemma and plumbing.