FAST L4 Redirect

No. That iRule is incompatible with fastL4. When using fastL4, most packets in a flow are not processed by TMOS directly, so you cannot utilize most iRule events and primitives. You will need to use a Standard VS.

By the way, with 11.5.1 performing a redirect, I recommend considering Local Traffic Policies:

• SOL15085: Overview of the Local Traffic Policies feature