Safe speed upscaling

[Shiraito983]

let's say Character A is about Hypersonic speed
and there's Character B who can easily sneak into Character A private space.
toying him and being unnoticed every time Character A tries to look in Character B's direction by displaying sheer speed

what is the safe multiplier for Character B?

 

[DaReaperMan]

Depends on how far they are to Hypersonic, but if you're tickling the balls of the speed tier, they'd go baseline Hypersonic