The anatomy of a 'bow'.

[D_o_S]

pay close attention the the pics in this link

as there is only one proper way to install the top

http://www.cooling-masters.com/articles-45-1.html

Ya, I realize that there is only one way to install the top...

However, when I tighten the screws, I can get a bow in two directions, can't I?

Screw pattern:
TL-----------TR
BL-----------BR

Scenario A:
I tighten down TL-BR-TR-BL.... I get a bow going from where to where?

Scenario B:
I tighten TL, BL, TR, BR - bow from left to right

Scenario C:
I tighten TL, TR, BL, BR - bow from top to bottom....

So, which one? Or have I got something wrong?