I think a horizontal split would be nice. I use both but have then docked and move back and forth to correct things.
 
If I could have the staff on the top and the piano roll at the bottom it would be great. You can of course do this now.
 
1. Close the multidoc or doc it to the main sonar window.
2. float the staff view and the prv and size them as you need.
3. save this as a screenset in your project and lock the screenset.
 
If you do these things you will be able to get back to this look any time you need to. You may need to select the midi track you want to edit in each window after switching to this screenset from another.
 
HTH
 
P.S. I gave you 5 stars because I think have a hybrid window would be simpler.

I like the idea, but I'm wary of all the things that would break with the first 3 or 4 releases afterwards...
 
Dan
 

Perhaps rather than changing the existing Staff and Piano Roll Views an additional view that is a hybrid of the 2. That way if something was broke about the new hybrid view perhaps it would not break the other 2 views and we would be able to continue working wile the bugs get sorted.

https://products.zplane.d...ng/vk2_hybridscore.png

The best example I have ever seen of this is Zplane's "hybrid score" view in their Vielklang 2 auto-harmonizer.