Sorry a not all undestod therefore i show some screnshot.
Horizontal spliting....we have tablet list of file from up side to down, and two split containber up for file on disk, and down side for write. All good but IMHO its not optimaly, we lost many workspace for horizontal of monitor. The part of usabiliti space are not used. And its on 4:3 side monitor. on 16:9 its part been bigger.
http://vbkesha.prgr.org/img/img_horizontal.JPG
If we have vertical split, at the same display of files we see more files without scrool and IMHO this a more conveniently in to use.
(i try to paint ho to view vertical split and nero for sample)
http://vbkesha.prgr.org/img/img_vertical.JPG
http://vbkesha.prgr.org/img/nero.JPG