The top chassis section alone doesn't locate the mb. The mb is located really be the entire frame with the exception of the bottom section. The mb compartment is a "C" shape and is extremely strong. Take a look at this STH10 pic. It is a bit easier to see what I'm talking about in this picture.
On the SMH10 is it the same exact design, but instead of the upper mid-plate, the top of the "C" is the top chassis section.
You may find the bowing the 140.4 mount or the roof will be difficult (unless I'm misunderstanding you.) This is especially true because the radiator acts like a giant stiffener. Hmm well some motorcyclist will heat up their radiators to bend them, but that's pretty risky stuff. Sounds interesting though.
Do you mean a 120mm top cover with a solid top and vented sides?
HDDs and SSDs don't really need much cooling. Passive air flow is really all you need. This is the reason for the ventilation on the front cover. But to each is own Edited by Kevin_CL - 11/2/13 at 1:04pm