Accord, when I first built my Impulse PRO, I had the same problems as you did with these pivot balls.
Serpent came out with a special tool to fit these pivot balls into the upper rear arms the same time when the 705 came out. It should be included in the kit. Check the bags where the supplied allen keys are. I think it's there. Part number is 902310.
As in the picture, you simply screw the allen into the small aluminum block. As you screw it in, the pivot ball will be pressed into the upper rear arm. Once the pivot ball snaps in fully, unscrew the allen out of the aluminum block
http://www.mytsn.com/products/product.asp?prid=2636