I was looking for a way to easily distinguish between charged and flat batteries in my field bag. The easiest system I could devise was to cap them when charged and then leave them uncapped after I fly.
I have tested this cover on my batteries. It seems the XT60 connector itself varies in size. Probably due to high temp soldering or hobby king manufacturing. If anything the fit gets more snug.
I included a hole on on the base of the cover. If the cover gets stuck for some reason this can be used with a small screwdriver or allen key to push the connector out.
Print 1 and make sure it works on your batteries. Then I made 10 packs, printing 10 at a time.