Setup OpenSIPS as B2BUA

Hello,? We have telephony application (you can think as UAC) and currently trying FreeSWITCH as proxy server but having issues in handling attended transfer. My feeling is OpenSIPS in B2BUA mode can help us much better. ? On FreeSWITCH,we use carrier(SIP trunk provider) to make outbound calls and currently have freeswitch which registers carrier as external gateway and my applciation as internal gateway. Use of FreeSWITCH will be optional with OpenSIPS and we need to find the best way for setup and if you have experienced with both then it would be great match for me. This setup has to be done in CentOS [login to view URL] is urgent requirment and looking for very experienced perosn who have done this. ? thanks