Wow... it is missing from 4.0.19
Yes, your instincts to put it in /customer/home.tpl are correct.
Here is where it lives in 4.1.x stock configs (in home.tpl):
Code:
{* $Id: home.tpl,v 1.88.2.4 2006/10/13 10:41:21 svowl Exp $ *}
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
{if $printable ne ''}
{include file="customer/home_printable.tpl"}
{else}
{config_load file="$skin_config"}
<html>
<head>
Right on top, before <html> (where it belongs).
Download a copy of 4.1.5 just to compare.