AppleScript to open four iTerms along the center of the screen instead of the corners

gistfile1.scpt

tell application "iTerm"
	set gap to 4
	set mw to 640
	set mh to 400
	
	set top_left to (make new terminal)
	tell top_left
		launch session "Default"
	end tell
	
	-- make some variables with data gathered from the first term
	set {x1, y1, x2, y2} to bounds of the first window
	
	set h to y2 - y1
	set w to x2 - x1
	
	set the bounds of the first window to {mw - w - gap, mh - h - gap, mw - gap, mh - gap}
	
	--------------------------------------------------------------
	set top_right to (make new terminal)
	tell top_right
		launch session "Default"
	end tell
	set the bounds of the first window to {mw + gap, mh - h - gap, mw + w + gap, mh - gap}
	--------------------------------------------------------------
	set bottom_left to (make new terminal)
	tell bottom_left
		launch session "Default"
	end tell
	set the bounds of the first window to {mw - w - gap, mh + gap, mw - gap, mh + h + gap}
	--------------------------------------------------------------
	set bottom_right to (make new terminal)
	tell bottom_right
		launch session "Default"
	end tell
	set the bounds of the first window to {mw + gap, mh + gap, mw + w + gap, mh + h + gap}
	activate
end tell