Eat a ton of protein...you will need it! I noticed my best gains in muscle and leaning out when I was doing less volume (not this program), Mon-Fri IF and eating a crap load of protein. Of course if you really want to pack on glycogen loads on the weekends with minimal pwo carb meals that should also add to muscle "size".
An interesting variation I played with was strength workouts Mon-Wed (split upper/lower compounds) w/ small pwo carb/protein and Fri full body complete depletion (glycogen) with high volume....and then a night of margheritas and steak, plus higher carb meals weekend lower protein (Basically a spin off Body Opus stuff). It worked pretty well....minus the hangovers and the $200 I spent at the strip club after the margheritas.