Hismith machine rigged for ball busting

[jhonson3232]

Hello all!
So I'm into busting my balls and also have a hismith machine so I figured 'why not combine the two'.

My initial thought was to attach a tennis ball to the end but it ended up not having enough force behind it. I'm going to experiment this weekend with a few different setups but was wondering if anyone had ever tried this before or know of any good attachments (purchased or homemade) that can help the Hismith pack the proper punch!
Thanks,