I’m definitely running into an issue; I’m not sure how to formulate a question. It’s not a compile error. It’s more of an “architecture issue”; I feel like I’m trying to cover a 10x10 floor with a 8x12 rug.
It brings me back to How to Compose Janestreet/Bonsai components?
Could you add a section on composition to https://github.com/janestreet/bonsai/tree/master/docs/guide ? 
Either I am missing something obvious or this is something non-trivial to pickup from the examples since the “architecture” often gets buried by the “low level technical details”