Taking one character off of {SysSerial}

[CSIT]

All,
I am a rookie PHP and C#/Java programmer, and a fulltime SysAdmin, so perhaps my coding skills are failing me. I am in need of assistance regarding a recent problem in our naming conventions and some join-to-AD problems.
We have an environment where we have multiple sites, and for the first time we have 10 sites using the same $siteName prefix, ie $siteName1, $siteName2, etc etc, so at $siteName10, we have ran into the problem that using the full {SysSerial} generates a ldap name that is 1 character too long. Thus we have decided to try to modify the SysSerial to only reflect the last 6 characters of the serial, instead of the full 7. I have scoured the forums, and even tried writing some c++ in the HostNameChanger service, but to no avail. This is, I believe, leading to our issues with joining to the domain.
The behavior that we ARE seeing is that the computers simply get their name changed, and do not attempt to join to the domain. We are also open to suggestions as to what else could be behind this.
Thank you all so much for this project, It’s been a life saver.