Multilink on Cisco routers

I have a core router that has multiple T1 lines going to it, one remote site has two T1's bonded and several other sites just have two T1's load balanced. If I wanted to convert some the load balanced T1's into true bonded T1's would I just add several more multilink entries? I created a sample config below. Also, is there an advantage to bonding T1's instead of just load balancing them?

Thanks

interface Multilink1
 ip address x.x.x.x 255.255.255.252
 ppp multilink
 ppp multilink group 1
!
interface Multilink2
 ip address x.x.x.x 255.255.255.252
 ppp multilink
 ppp multilink group 2
!
interface Serial1/0:0
 no ip address
 encapsulation ppp
 ppp multilink
 ppp multilink group 1
!
interface Serial1/1:0
 no ip address
 encapsulation ppp
 ppp multilink
 ppp multilink group 1
!
interface Serial2/0:0
 no ip address
 encapsulation ppp
 ppp multilink
 ppp multilink group 2
!
interface Serial2/1:0
 no ip address
 encapsulation ppp
 ppp multilink
 ppp multilink group 2