Strangely, I'm with robert on this one.
Maybe it's because saying that you don't need isolation to maximize hypertrophy is like saying you don't have to eat meat or protein supplements because you get enough protein from beans or eggs. Or that you don't have to deadlift to get a stronger deadlift. Which are sort of true, you can do that. But if you have a goal to achieve something as fast and good as possible, why would we deny that chance?
Yes, OP is quite lightweigth, he can't build huge arms to a 60kg body. That's understood. You have to eat a lot and do compound exercises, that's a given. But if a client/athlete wants bigger arms, then hell, I would add arm work to the program. And it will make a difference. No BB Rows will not work as well to build bigger arms than actual arm training. By adding arm work, you
1: Get more frequency, your arms get to work more, and more often.
2: Get more volume, more reps and sets in addition to all rows and pulls.
3: Increase time under tension for said muscle, more work, more stress, more fatique, more muscle damage.
And suprise suprise, these are some of the main factors of HYPERTROPHY.
Doing isolation work means roughly 5-10 minutes from a workout, if that. A couple of sets. Maybe a superset of exercises. Nothing more is needed. Not like you need an actual arm day to get your guns to grow. If you are really serious, want big improvements and have a little cash, go to the pro. Dan Trink has build one high-rated arm workout protocol: Two ticket's to the gun show.
http://www.trinkfitness.com/2-tickets-to-the-gun-show/" onclick="window.open(this.href);return false;