Adding additional flat rate

I want to have two flat shipping rates ; one for next day delivery (fix price) and one for same day delivery (fix price).
I've made in every shipping directory a new file flat2.php.

When I want to install I receive an error in admin : "Fatal error: Class 'ControllerShippingflat 2' not found in /home/kirrikirri/domains/kirrikirri.co.uk/public_html/daminex/shop/admin/controller/extension/shipping.php on line 125"

Anyone an idea how to solve ?

PS. version 1.5.3.1

You don't need to duplicate the flat rate shipping method, just use Weight Based Shipping as I describe in this topic:

http://forum.opencart.com/viewtopic.php?f=114&t=86202