3-D Print or Vacuum form? Are you kidding me? If I can afford all that then I can most def afford some $40-$50 OEM Makita replacement batteries and have to waste my oh so valuable time on this bit if DIY self-stroking.
Dude, you can get replacement Makita batteries for ~$15 on eBay. The LiPo battery alone that you used costs way more than that. Then there's the $400 - $500 worth of equipment needed, like the high end hobby charger, your high end soldering station and your extra fancy wire stripper. Plus, there all the issues with LiPo safety. Clearly you do not cut corners, but I bet others will and Pop Goes the Battey and Boom They're dead.