Today, foreign names are anglicized more or less systematically from their original spelling: the Russian surname "Петров" generally becomes "Petrov", not the calqued "Peterson" or the more phonetic "Petrof" or "Petroff" (which reflect final-obstruent devoicing). The phonetic type of surname anglicization was apparently in style at least as recently as the early 1900s, when Rachmaninoff (Рахманинов) started coming to the United States.
Insofar as writers sought to anglicize -в surnames by their sound, what norms and influences guided the choice between -ff and -f? Was -ff influenced by German or French orthography? Does -f "look wrong" to some readers? Is the -ff supposedly a longer sound, and if so, why would one be called for? Was either spelling ever more canonical?