ahem.
Given all the different hubs people are attaching to XR rails it makes sense to sell spacers to allow another size of rail width. Not exactly clear how much wider or even what size battery the goal should be.
well the idea of stackable spacers and printing your own box easily is cool because there could be lots of adjustment and variation, but the issue of the outside bumpers needing to fit would have to be solved. So just going for one extra width and making a special bumper or floatplate. Not to mention needing mods for fitting fenders and fins.