Having just been through the spring issue, I thought I'd share what I did.
First, only 6-32 screws fit (properly) through the latest mobo's holes, which have a diameter of 0.150". There is still one board out there that uses the old spec of 0.210".
I got a set of 6 lb springs from McMaster. Since the max clamping force is 24 lb, with a minimum of 12, and 18 being typical (as per AMD spec), and since I have 4 mounting points, well, do the math!
The thing about springs though... is that they all have very specific ratings, and usage conditions.
They will give you a fixed amount of force, in proportion to how much they are compressed.
My springs could be compressed all the way down (indeed turning them into spacers), but that would push them beyond their rating. Pushing a spring beyond it's rated force will actually damage it, and it eventually won't react the same as when it was brand new.
Not using any springs is OK, but you then have very little play, to reach the right clamping force: where you would have to turn a nut a number of turns to reach 6 lbs with springs, you might go over 6 lbs very easily with a very small fraction of a turn, without springs. I doubt that those people that do not use springs, even bother to use a torque wrench
In retrospect, I would have opted for springs rated a bit higher than 6 lbs: more like 7.5 to 9 lbs. AMD specs also allows a maximum of 30 lbs clamping force, when using the 6 side tabs (why? I dunno, but I don't really care either, it's just nice to know that I can go over a little).
When choosing a spring, it's also very important to pick one with an inner diameter that's as small as is possible, to avoid having it twist sideways around the mounting screw.
Also picked up from some of BillA's work: the block has a weight (!) and it actually factors in the equation of the clamping pressure.
Note also that "hose tugging" can be quite deadly to a CPU core.