One thing which bothers me from the very beginning of this strange "ping" discussion: who says the latency of the ping signal is the same as in clear sky and fully operational device?
These southern and northern arcs are derived from a time delay measured from a satellite and calculated straight forward. BUT, how says there is nothing obscuring the delay, i.e. covers are known to delay these signals and maybe the device aboard is not fully functional, even a torn wire will put additional latency? So, conclusion: these arcs are the max. distance from the satellite, not necessarily the most probable. With this, the plane can sit anywhere on half the world.
This speculation is not less probable as all the others, or?
BTW: 45 south? I find it hard to believe that MH370 could come that far. How many abandoned ships float there in the roaring forties?