Hi!

Actually it is rigctld that is the limit. Cqrlog passes extra command line arguments as a string to rigctld start command without checking numerical base.
From rigctld man page:

-c, --civaddr=id
Use id as the CI-V address to communicate with the rig.

Only useful for Icom and some Ten-Tec rigs.

Note: The id is in decimal notation, unless prefixed by 0x, in
which case it is hexadecimal.

So putting "-c 0x76" to extra argument line will do it in hex.

And there is no need to think about wsjt-x settings. Start cqrlog first with parameters you need.
After that start wsjt-x. Manually or via cqrlog remote.
Rig parameters for wsjt-x are then:
rig = Hamlib net rigctld
Network sever = localhost:4532
PTT method = CAT
Rest of settings depending rig properties.

That way wsjtx will use same rigctld what cqrlog has already started. No collisions in rig serial line.