title: MacVim+NERDTree: How to open a file as a split in furthest horizontal split
body: <p>I've been browsing mvim docs and have tested out the various commands, but I can't seem to find one that solves my issue.</p>
  
  <p>Here is what I have:</p>
  
  <pre><code>/========================================================\
  |          |                      |                      |
  |          |                      |                      |
  |          |     file 1           |                      |
  |          |                      |                      |
  |          |______________________|                      |
  | NERDTree |                      |     File 3           |
  |          |                      |                      |
  |          |    file 2            |                      |
  |          |                      |                      |
  \__________|______________________|______________________/
  </code></pre>
  
  <p>What I'd like to have:</p>
  
  <pre><code>/========================================================\
  |          |                      |                      |
  |          |                      |                      |
  |          |     file 1           |       File 4         |
  |          |                      |                      |
  |          |______________________|______________________|
  | NERDTree |                      |                      |
  |          |                      |                      |
  |          |    file 2            |      File 3          |
  |          |                      |                      |
  \__________|______________________|______________________/
  </code></pre>
  
  <p>I'm able to move things far right, into a new vsplit, as well as far top and far bottom.</p>
  
  <p>New NERDTree files are opening by default in the File 1/File 2 vsplit.</p>
  
  <p>Any help is appreciated, thanks!</p>