react native - Is it an acceptable structure to nest Navigator components? -

i have mobile app flow this:

1. user loads app, presented login/oauth screen
2. there other scenes in stack pushed on top of (sign up, forgot password, etc) - related scenes
3. no tabbarios @ point

once user authenticates, they're taken totally different screen has tabbarios @ bottom switch between (for example) messages, settings, news, etc. if on news tab (listing of news item) , user taps news item view article, detail view pushed onto stack tabbarios remains visible.

so have 1 main navigator @ root level swap between login/signup stack, , "user logged in" stack, , have navigator within user can navigate around in news articles.

i'm wondering if bad pattern in react native , if there's better way, or if spot on.