LANMonkey
Use SME8beta6 (based on CentOS 5.5), it is quite stable in it's current form, if you need the newer Centos OS with the SME interface, then this is the only answer.
It would be a MASSIVE job to re-engineer Centos 5.6 to drop SME into it, if you want to do that then you should really join the dev team and get SME 8 completed (to final release) and work on moving to Centos 5.6, which will be inevitable anyway.
Working to finish SME8 would be a far easier and less time consuming task than dropping SME into Centos 5.6.