8 is traditionally Justice, and 11 Strength or Force. AE Waite popularized the switch to 8=Strength in the early 20th century, based on the Golden Dawn theories. But the second-most-famous deck, Crowley's Thoth, reverted to the traditional numbering, and the Marseilles tarot (the most influential in continental Europe) naturally kept the original numbers because it's where they came from. There's no need to make 8=Strength unless you prefer it that way, as either is valid at this point in time, depending on one's preference.