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
refhpos means a distance from the left paper edge, but
lochpos from the right paper edge. So you would have to calculate, substracting
\paperwidth to get your new
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.
You could use
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.