Yes. It will support any number of SRs. You will need to update the drbd, lvm, iscsi-ha and tgt config files to add the additional resource.
See this post for details.. It is quite lengthy, but all the steps are there. ALso, depending on your version, the tgt target config may be in a different location. It will be one of the following:
/etc/tgt/targets.conf
or
/etc/tgt/conf.d/ha-targets.conf