For the chins, I would try to hit 10 on all sets. use the lat pull down and just raise weights each time you do them. I would also alternate with rows.
I'm thinking about adding 5-3-1 for a back excersize as well, something like
press 5-3-1
bench 5x10
rows 5-3-1
chins 5x10
and switch on the bench day. I don't think it would push me so much more as to take away from the other lifts.