Vertical position: Obviously locvpos
has a value of 0 pt with your style, which is common for many letter styles. You could set it yourself or use toaddrvpos
instead.
Horizontal position: refhpos
means a distance from the left paper edge, but lochpos
from the right paper edge. So you would have to calculate, substracting lochpos
and locwidth
from \paperwidth
to get your new refwidth
.
Width: You can simply use locwidth
as you did, perhaps the option refline=narrow
could be useful for you in addition.
Since you design the template yourself, you don't have to use predefined values, you could set your own.
Example:
\documentclass[refline=narrow]{scrlttr2}
\setkomavar{yourref}{Z7H88}
\setkomavar{yourmail}{10/28/2011}
\setkomavar{myref}{A124}
\setkomavar{customer}{42}
\setkomavar{invoice}{I-2011-22}
\setkomavar{date}{11/01/2011}
\usepackage{calc}
\makeatletter
\@setplength{refvpos}{\useplength{toaddrvpos}}
\@setplength{refhpos}{\paperwidth-7cm}
\@setplength{refwidth}{3cm}
\makeatother
\begin{document}
\begin{letter}{Reader}
\opening{Dear reader,}
\closing{Yours Sincerely}
\end{letter}
\end{document}

Another approach
You could use
\setkomavar{location}{...}
to use the location field while designing your own reference fields block therein, not using the predefined reference fields. So you don't have to change position and width.