I purchased a used set of Cusco Zero 2E coilovers and one of them is making a metallic "clunk" noise everytime I hit a bump.

I think the noise is coming from the pillow ball bearing in the uppermount.

Zero 2E's come with their own tophats:

However, I know certain coilovers don't come with tophats/uppermounts and the owners reuse the stock ones:

Can I do this with my Cusco's?

This is my first experience with coilovers, so it seems as if it should work but I want to know for sure before I attempt it.

I also found these upper mounts from Cusco, which I will probably end up buying, but I want to try the factory top hats first just incase the clunk is not from the pillow ball.
Cusco Front Pillow Ball Upper Mounts Subaru WRX / STI 2008-2014 / Forester 2009-2013 692 410 A at RallySportDirect.com

I already tried re-torquing all of the bolts, adding a little preload to the springs, different dampening settings, and tightening the topnut. Nothing has helped so far.

If anybody has any input it would be much appreciated!