Ok Dwight, here you go...
As I mentioned on this thread or the other one, I use the Impact Clamps because of the low profile handles so I can use them closer to the wall and still be able to tighten them, and price, and I like them fine. Keep in mind that with these booms, you want to be able to rotate the entire mount around the post to get best positioning. The Manfrotto handles hit the wall as soon as you rotate the mount closer to the wall. With these Impact clamps, you do need washers to fill the extra space because the holes are not quite as deep. With the manfrotto clamps, no washers are needed. My washers are too big, btw, I'll fix that later.
Again, the screws are 5mm x 16mm long, hex drive, and you'll need two per clamp, four per boom. These are basically the same screws that they include with Expan paper system to secure the paper hanging brackets.