In ElasticXL, Sync is a normal bond in every way except its name. In clish, it's bonding group 1024. You can add any interface you want, and you can remove the default interface.
When running VSNext, Sync is owned by VS0. The other VSs don't see it.
[Expert@DallasticXL-s01-01:0]# gclish -c "show configuration" | egrep '(^[0-9]|bonding group 1024)'
1_01:
add bonding group 1024
set bonding group 1024 mode active-backup
set bonding group 1024 primary eth1-Sync
set bonding group 1024 xmit-hash-policy layer2
add bonding group 1024 interface eth1
add bonding group 1024 interface eth1-Sync
1_02:
add bonding group 1024
set bonding group 1024 mode active-backup
set bonding group 1024 primary eth1-Sync
set bonding group 1024 xmit-hash-policy layer2
add bonding group 1024 interface eth1
add bonding group 1024 interface eth1-Sync
[Expert@DallasticXL-s01-01:0]# cat /proc/net/bonding/Sync
Ethernet Channel Bonding Driver: v3.7.1 (April 27, 2011)
Bonding Mode: fault-tolerance (active-backup)
Primary Slave: None
Currently Active Slave: eth1
MII Status: up
MII Polling Interval (ms): 100
Up Delay (ms): 200
Down Delay (ms): 200
Peer Notification Delay (ms): 0
Slave Interface: eth1
MII Status: up
Speed: 1000 Mbps
Duplex: full
Link Failure Count: 2
Permanent HW addr: 00:1c:7f:ab:cd:ef
Slave queue ID: 0
As you can see, rather than renaming an interface to eth1-Sync, I've added the interface named eth1 to my Sync bond.