cool tank!
I understand your concern about adding Finley to this calm setting.
You can only judge for yourself if it's worth the risk of upsetting the rest...
I spend quite some time finding a combo of fish that will look nice, but foremost act friendly.
i had several aggressive fish before, but the chasing down and hurting eachother spoils my fish-watching-fun.
So i'm not adding anymore fish, nor changing the combo, for it's finaly a good one.
Does your pleco have his own cave yet?
Seems like he's looking for one.