Use of FPV is to be avoided if the reason for the unreliable speed are the static ports. Many simulators cannot simulate this failure, they only simulate pitot freezings and you may come to the conclusion that the FPV always gives a good indication.
Which makes me think of a question: in the ureliable speed procedure we have to level off and use the tables and then be able to troubleshoot. But how can we be sure that we are maintaining an altitude? If we have GPS available we can check the GPS page, but if not, how can we rule out a static problem?