this AppleScript positions 2 windows (ex. text editor and terminal) in ratio of 8:2 vertically

spliter.scpt

tell application "Finder"
    set display_size to bounds of the window of the desktop
end tell

(* bounds == {0, 0, width, height} *)
set width  to item 3 of display_size
set height to item 4 of display_size

set editor   to { name : "Sublime Text", top : 0,            height : height * 0.8 }
set terminal to { name : "Terminal",     top : height * 0.8, height : height * 0.2 }

tell application "System Events"
    set position of first window of application process (name of editor)   to { 0, top of editor }
    set position of first window of application process (name of terminal) to { 0, top of terminal }
    set size     of first window of application process (name of editor)   to { width, height of editor }
    set size     of first window of application process (name of terminal) to { width, height of terminal }
end tell