actually I watched 1 US food channel the chef deep fried steak (beef)
he using about 10mm thick steak to deep fried for 5-8mins.. he used rib eye marinade about 30mins+, put the beef cover by some flour then put egg n cover by flour again.
He said If just only 1 layer flour beef'll be hard to chew n dry.. but using 3 layer it can keep the beef tender and juicy.