Compound movements yes, but not 6-8 range. That's not enough work for the muscles in order to stimulate muscular growth. More like 10-15 reps a set, squeezing and holding the muscle in its contracted position for about half a second each rep.
Think about it - you do say 4 exercises per body part for 3 sets of 15 reps (on average for the sake of argument) - that a total of 180 reps per body part. Half a second squeeze each rep means the muscle is in it's contracted position (time under tension) for a total of 90 seconds. Add to that the negative part of the rep which is where the muscle gets torn down and you've got yourself a proper workout where the muscles have suffered significant stimulation in order to grow back bigger (with diet and sleep of course, plus drugs if you decide to go that way).
6-8 reps in a set simply won't cut it. You'll probably get stronger that way, but not bigger.
the contracted position isnt eh position that makes it grow. the position where its strongest, and handles the most force, is the sweet spot.
and when i say force, i mean amount of work in a certain time..
so for biceps its easy, its the mid point in a curl- thats when the weight has the greatest force, AND when the biceps is strongest.
for pecs, its just past half way for most people, the point where the elbows are the greatest distance from the body but not lower than the body (thats when its mechanically disadvantageous).
free weight flyes are only stimulating for about 1/3 of its range..the other 2/3 the weight is either above you, or bringing your elbows below you.. pretty useless exercise really.
why would anyone want to spend their energy on portions of a rep that arent useful?..