eledmac: facing pages with glossed text using covington.sty

Question

What I'm trying to do:

I am attempting to create a document using eledmac/eledpar with facing pages. The left page contains a glossed text using covington.sty and the right page contains a prose translation.

Because each line of glossed text takes the space of two lines of text, the right text doesn't line up.

What I'd ideally like:

.……………………………………………………………………………………………………………………………………………………………………….
|                               |                                |
|           Left Page           |           Right Page           |
|                               |                                |
|  1 foreign words here         |    running translation goes 1R |
|    glossed words here         |    here and continues etc.  2R |
|  2 more foreign text          |                                |
|    more glossed text          |                                |
|  3 next chunk of text         |    running translation of   3R |
|    next gloss of text         |    next chunk here.         4R |
|                               |                                |
=                               =                                =

What I'd gladly settle for:

(Because it may be impossible to get eledpar to add extra lines on the right without tricking it to think they're there on the left!)

.……………………………………………………………………………………………………………………………………………………………………….
|                               |                                |
|           Left Page           |           Right Page           |
|                               |                                |
|  1 foreign words here         |    running translation goes 1R |
|    glossed words here         |    here and continues etc.  2R |
|  3 more foreign text          |                                |
|    more glossed text          |                                |
|  5 next chunk of text         |    running translation of   3R |
|    next gloss of text         |    next chunk here.         4R |
|                               |                                |
=                               =                                =

MWE:

%!TEX program = xelatex
\documentclass{book}

\usepackage{fontspec}
\setmainfont{Hoefler Text}

\usepackage{eledmac,eledpar}
\linenumincrement*{1}
\firstlinenum*{1}

\usepackage{covington}
\newcommand\ml{\gll}
\newcommand\mll{\gln \glend \smallskip}
\newcommand\nl{\mll \ml}

\newenvironment{itside}{%
    \begin{Leftside}%
    \beginnumbering%
}{%
    \endnumbering%
    \end{Leftside}%
}
\newenvironment{engside}{%
    \begin{Rightside}%
    \beginnumbering%
}{%
    \endnumbering%
    \end{Rightside}%    
}

\begin{document}




\beforeeledchapter

\begin{pages}

\begin{itside}

\pstart
\ml Imbelli Dei! su via, scagliate il vostro
    cowardly gods up away throw the your
\nl più fatale rigor! Non pave l'alma.
    most deadly severity not fears the.soul
\nl Se costretto son io, fra vili spoglie,
    if constrained am I in vile clothes 
\nl errar fra queste selve,
    to.stray through these woods
\nl profugo e sconosciuto,
    fugitive and unknown
\nl un dì saprò punir de' miei vassali
    one day I.will.know to.punish of.the my vassals
\nl i ribelli tumulti, indi più fiero,
    the rebel riots then more proud
\nl ascenderò sul trono,
    I.shall.ascend on.the throne
\nl se Licaon e re d'Arcadia io sono.
    if Lycaon and King of.Arcadia I am
\mll \pend

\pstart
\textbf{Some non-glossed text here}
\pend

\pstart
\ml Oh quanto bella gloria
    oh how beautiful glory
\nl è quella del cacciator.
    is that of.the hunter
\nl Ha sempre la vittoria,
    has always the victory
\nl né vinto è dall'amor.
    nor defeated is by.love
\mll \pend
\end{itside}

\begin{engside}

\pstart
Cowardly Gods! arise, throw your deadliest severity at me!
My soul is not afraid. If I am forced to wander through these woods in vile clothes,
fugitive and unknown, one day I will know how to punish the rebellious rioting of my vassals,
and then, with greater pride, I shall ascend to the throne, if I am Lycaon and King of Arcadia.
\pend

\pstart
\textbf{This should line up with the non-glossed text}
\pend

\pstart
Oh how beautiful is the glory of the hunter. He always has victory, nor is he defeated by love.
\pend

\end{engside}
\end{pages}

\Pages

\end{document}

I have tried to add some of line printing/processing macros from eledpar into my convenience macro \mll but they don't seem to have any effect.

What should I be doing?

Any help gratefully received!