The standard Roughstack is sized to fit an 18350 battery, with no additional room, so you'd have to use the Maxi Roughstack, which is sized for the 18650. I will work with the 18500, but you would have to add a spacer to use a 18350. Using the Maxi RS may defeat your purpose for smallest size, as it is exactly the same height as the mini Lavatube. I don't have a Vamo to compare when using a 18350.