The important thing about spacing and scale is that it needs to be even for @2x so that you can halve it for @1x. So you can do 4px/2px, or 6px/3px, but not 5px/2.5px. I usually use 4px/2px or even 8px/4px to keep things even throughout the tileset.
Also, with the things Dusk has in place to remove tile flickering, you only need to add spacing and set the texture filter. Dusk ought to take care of the rest. If you use spacing and (for some reason) you still see flickers after setting the texture filter and everything, you’re able to extrude the tileset anyway because you have several pixels of room between tiles (another good reason to use 4/2 or 8/4 instead of 2/1 spacing).
- Caleb