Damage3245 said:
We have a panel of them going seemingly going FTE once; that isn't proof that they maintained that speed constantly over the entire journey.
Trying to estimate the distance by assuming constant FTE travel speed would lead to a heavily inflated size.
Disagree with this. Nothing in the verse says they'd not be able to. Even Shunshin itself doesn't pose a limit other than chakra:
Body Flicker Technique (Shunshin no Jutsu)
Ninjutsu, D-rank, Supplementary
Users: Gaara, Hatake Kakashi, et al
A movement technique with extreme speed like a gust of wind!!
Appearing along with the wind, disappearing like the wind: the ninja's instantaneous movement technique. This super fast movement is almost impossible to grasp with the naked eye. If seen by an ordinary person, it would seem as if the user has teleported… In reality, the user has vitalized his body with chakra and moved at super speeds. The amount of chakra used up differs depending on the distance and elevation of their stopping point in comparison to the starting point.
The cloud of sand dances in the wind…
Haku's and Kakashi's Body Flicker. Dancing leaves and disappearing in an instant like mist.
There are many variations of the Body Flicker for the various villages and user. Gaara's use includes the Sand Body Flicker. There are also the Mist Body Flicker, Water Body Flicker, and Leaf Body Flicker, among many others.
Characters in verse that aren't particularly noteworthy in most cases have even demonstrated being able to travel greater distances in minutes via shunshin such as Juugo and Karin.