Unfortunately, getting a stock Sony CP to authenticate is not just a matter of editing some URLs - it uses an entirely different authentication mechanism than regular chumby devices.
Upon boot, the Sony middleware contacts a Sony server that downloads an XML manifest, which for the dash included a special token that correlated a data record on the Sony Style service with a chumby account - basically the Sony server told us which account to use for widgets, and they handled the same for the video and audio services (Netflix, etc). That correlation would occasionally fail, resulting an unfortunately common but confounding error called a "device/suit mismatch" that required direct manual intervention by Sony to correct.
The dash also supported an odd "use without activation" system which was fraught with problems - it created a sort-of "anonymous" account on the chumby systems that never really worked well and were difficult to provide customer support for since we couldn't figure out what account belonged to a user that contacted us for help.
The Sony server no longer responds to the middleware request. One of the more fundamental things that the Chumby CP for dash does is use the standard chumby-style (internally called "DLA") authentication, including the very successful "ovals" activation system.
The rewrite of the chumby servers that I did a few years ago removed all of the code that was used to support the Sony authentication, which greatly simplified things.