Problem Loading Eguile Templates

[newtognucash]

I'm having some difficulties with customising eguile templates.  I'm
running version 2.4.10 on FreeBSD.  Said version includes the extra
eguile templates taxinvoice.scm and balsheet.scm.  So far so good...

I want to customise the invoice template for my own needs, and as such
don't want to have to re-customise it every time I upgrade to a new
version of GnuCash.  The obvious thing is to follow the steps in
loading a custom report as given here:
http://wiki.gnucash.org/wiki/Custom_Reports.  I copied the
taxinvoice.scm and associated files into my .gnucash folder, renamed
them as "mycompanyinvoice.scm", etc., listed them in the config.user
file for loading into GnuCash and redefined the .scm file so that it
is unique and listed as a separate report.  It now shows up in the
Reports-Business menu as "My Company Invoice".  Next I changed a few
of the options in there to have them appear how I wanted -- the
heading font for my company name, etc.  I save that, reopen my GnuCash
file, and the changes have come through.  Excellent.

Next, I want to edit the eguile template file, since I don't want a
due date showing on my invoices.  Before I edit the eguile file, I
edit the mycompanyinvoice.scm file at line 141-2  It now says

(N_ "The file name of the eguile template part of this report.  This
file should either be in your .gnucash directory, or else in its
proper place within the GnuCash installation directories.")
    "mycompanyinvoice.eguile.scm"))

I save everything, reopen GnuCash, go to produce a report based on "My
Company Invoice", and I'm told

"Template file "mycompanyinvoice.eguile.scm" can not be read".

Hmm...  So my next guess is that the eguile.scm file has to be
uniquely defined in some way besides simply changing the file name to
make it work.  I can't find any documentation on this, though I've
spent hours searching.  I did try a few things myself, but haven't
found anything that works.  Does anyone have any suggestions, please?

Thanks a lot.

GnuCash Australian User