I think 4-5 full body workouts per week is too much, and prevents the muscles from growing faster than it actually can.
It is said that if you for example train chest on monday, you shouldn't train it until wednesday (48 hours later). That goes for most muscle groups when it comes to weight lifting. If you were training your back like 5 days in a row, the back wouldn't have enough time to restituate(sp?), and would go in a catabolic phase.
I'd do a 2-split, if I were you. Train monday, tuesday, thursday and friday.
Day 1: chest, triceps, shoulders, abs. Day 2: back, biceps, feet.
The reason I put chest, shoulders and triceps in the same workout, is because for example in bench press, you utilize all those muscles.