18650 improved spacer/holder

I attempted to use some 3D-printed 18650 spacers, but they weren't ideal. The injection-molded design you can get from aliexpress has two identical tabs on each side, which makes the other printed alternatives weaker. This updated module features:

• Larger, alternating tabs
• A looser battery fit
• A perfect fit for nickel metal grids

Note: Print two pieces and test the fit. Be sure to check the comments—some users report a perfect fit, while others find it too loose. Resize for perfect fit and share your experience.