RouterOS 4.11 on a RB133C

I’m bringing a new client on board tomorrow who has a 133C with a CM-9.

He doesn’t want to spend money on new equipment.
His current WISP won’t provide him with the user name and password for the router.

I’m going to have to netinstall.

Do I load 3.3 or 4.11?

Thanks.

We feel more comfortable with 5beta on RB133, it looks smoother.

I’m not prepared to run beta software in a production environment.