With HACMP 5.1/5.2/5.3/5.4 the procedure runs about like this:
- First: Make disks visible from all cluster nodes by running cfgmgr. The new disk devices "none None" should be visible then on every node. No need to keep device number identical though.
- Second: Create PVID on every disk from every node before you start to introduce them to the cluster. This can be done by a "chdev -l hdiskX -a pv=yes". Only the first time a pvid is written onto the disks. On the second node this command detects the pvid and uses it. I.e. you end up with new disks that can be identified by their pvid from every cluster node.
- Third: let HACMP (from the HACMP SMIT panels) discover the cluster node's new hardware.
- Fourth: use CSPOC to add a disk to an existing shared vg and then to extend LV and FS.
Can be done while HACMP (and the RG) is online.

Now to what you did....that could be done probably but seems to be too complicated to me. The AIX way of administration is somewhat different. Even with a SCSI2 protocal based VG there is neither a need to varyoff the VG from the primary node nor export the VG from the secondary node. You could do a Learning Import online. On primary you do
# varyonvg -b -u <sharedvg>
on secondary
# importvg -L <sharedvg>
and immediately afterwards on primary
# varyonvg <sharedvg>
This procedure was used in HACMP 4.x times. Mind that the Learning Import would be wrong for ECM VG. It also won't work after an exportvg as it expects the VG being known in the server already.
Obviously you stopped the cluster. That way there should at least be no problem with verifying and synchronising the cluster. Test it. After going live don't change anything.