The same duration multimeasure rests side by side are different lengths

[James Lowe]

Hello,

Consider:

\version "2.13.10"

{
  \compressFullBarRests
  \override MultiMeasureRest #'expand-limit = #2
  \override MultiMeasureRest #'minimum-length = #20
  R1*16
  R1*16
  R1*16
}

It doesn't really matter what numbers you use here, but I wonder if 
anyone could tell me how I can get the first instance of the multi 
measure rest the same width as the second one - the third instance just 
to check.

Thank you for your time.

James