We have a cluster of 120Gs with 7.2.9 (with HA port on port13), also a
100F and a 70F on our other offices also running 7.2.9 connected with
IPsec since 8/25, they have been working fine so far.
We had a related problem yesterday, setting up a new HA, the FortiGates
could see each other's serial number but unable to sync ("no route to
host"). I decided to abandon the HA ports and selected a different port
(port13) and HA synced up right away...