Clean up any flux you might have used and since the board is out you might as well give it a good clean with a electronic cleaner or high content isopropyl alcohol.

Reassemble the rumble pak and screw in the gamebit screws.

Having the battery compartment void of batteries causes you to hear the rattling of the battery terminals. I've invested in a set of 2 AAA dummy batteries to fill the compartment which will eliminate the sound by applying pressure to the once used battery springs. Anything can be used here really but I went for the exact fit in this case. The

rumble pak is relatively light without batteries and the dummy battery will help add some of it's original weight back.