starting the first page on the left [in 2.21]

[Kieren MacMillan]

Hi all,

I've got a two-sided page layout:

\paper {
  paper-height = 11\in
  paper-width = 8.5\in
  top-margin = 0.375\in
  bottom-margin = 0.75\in
  two-sided = ##t
  inner-margin = 0.625\in
  outer-margin = 0.625\in
  binding-offset = 0.25\in
  indent = 0.5\in
  short-indent = 0\in
  …

One of my pieces fits nicely on two pages, so I'd like to have it "reversed", 
i.e., page 1 on the left and page 2 on the right.

What's the most elegant incantation to make that happen? If possible, I'd 
rather not add a blank page, change first-page-number, etc. I'm using 2.21 
because the edition-engraver is currently flaky with ≥2.22.

Thanks,
Kieren.