See my post above on my reps. Next time you're in Russia, I'll show you 60 reps, then my workout partner will put me to shame and do the same thing with three 25 kilo plates hanging off his .... He actually does the pull up and the negative for over 20 reps.
That being said, my personal results have shown that for me, this approach worked. If he can do 20, great, that is his number for now. But if he keeps doing them periodically in his work outs, 20 just will not be enough.
Guarantee that if he does 60, he will not be able to complain that his back is not sore.
