I did this once before. You have to get into the code and change the part of the quoting portion of the code that goes something like this:
if ($free_shipping) {
output free shipping
} elseif ($module) {
output module
}
to something more like this:
if ($free_shipping) {
output free shipping
}
if ($module) {
output module
}
More specifically, you may just need to go to checkout shipping and look around line 112 or something for this:
if ($shipping == 'free_free') {
$quote[0]['methods'][0]['title'] = FREE_SHIPPING_TITLE;
$quote[0]['methods'][0]['cost'] = '0';
} else {
$quote = $shipping_modules->quote($method, $module);
}
and change it to something like this:
if ($shipping == 'free_free') {
$quote[0]['methods'][0]['title'] = FREE_SHIPPING_TITLE;
$quote[0]['methods'][0]['cost'] = '0';
}
$quote = $shipping_modules->quote($method, $module);
This may or may not work for you, and it may or may not be complete. It's been a long time since I've done it. Good luck.