> And of course the tetrameter version has a variable number of slacks.

Here's a scansion of part of the Paxton song.

I thought1 you were an A2rab3                   4
I saw the des1ert in your eyes2         3       4
I thought1 of ask2ing for a job3 in Abu Dha4bi
When you sprung1 the big surprise2      3       4
You hand1ed me the mon2ey3                      4
Like a real1 Arab does2                 3       4
I thought1 you were an A2 rab3                  4
And all the time1 you were the fuzz2    3       4

This sort of thing is extreme for a poem, but not for a song.

John Cowan <[log in to unmask]>
I amar prestar aen, han mathon ne nen,
han mathon ne chae, a han noston ne 'wilith.  --Galadriel, _LOTR:FOTR_