2.25.20 aligning text at end of multi-measure rest

[Paul Scott]

My MWE seems consistent with NR 1.8.2 Text alignment but how can I get 
text actually right aligned in a section of music?

\version "2.25.20"
{
  \compressMMRests
  R1*10^\markup\sans\right-align{ "poco accel." }
  \mark \default
  R1
}
TIA,

Paul