concern about it

[S0ULphIRE]

OOOOH, you mean the backplate is too thick so it's causing your motherboard to bend?

Well in that case, as fat.clown said, make sure you attach the risers to your mobo. e.g. these things:

 

[Burn]

my waterblock makes my board bend. i've asked several people about this and they've all said that bending is only a problem at the point of disfunctionality. So if you board bends a little and still works fine, i wouldn't worry about it too much

but, as soul and fatclown said make sure you are using all the standoffs

 

[geforce8800]

is that need to screw before the motherboard?

 

[Yami]

is that need to screw before the motherboard?

Yes, because it goes between the motherboard and the case.