AC33 is usually very full, in all three cabins, as the flight goes onward to SYD.

As [MENTION=29064]yyznomad[/MENTION] mentioned, 126, 128 depends on the day of the week. Based on my limited experience, 126, 128 usually have a few empty J/PY seats mid week, buy Y seems to be full all the time.

Another thing you may consider is that, AC126/128 usually lands much earlier than scheduled. the gate to gate time is usually under 4 hours. So Y may be survivable, I did it once in the preferred seat when AC156 was operated by A320.