Here is my attempt at the final stanza. (We have already done the stanza
which follows this as a 'postscript'.)

Here the poet seeks to have the whole pleasant experience repeated in
the future. "If you come by another book," he says, "pass it on and we
will write you another praise poem in return". There also seems to be a
suggestion that the future book (and therefore perhaps the Colum Cille
verses themselves?) might be the spoils of war. 

The poem closes with the opening line, as is the custom, but in doing so
the poet has had to force the rhyme a bit. '-mh' [in line (f)] does not
rhyme with '-n' and '-l' [in lines (b) and (d)]. By way of compromise he
has ended lines (c) and (e) in '-nn', which does consonate properly with
'-mh' [in line (f)] - but again not with '-n' and '-l'.

(a) Leabhar láimhe anfhîr
(b) ûaisle ina Traoi is Táin
(c) ferrde a ionnradh ûainn
(d) nî diongnADh a dhâil
(e) d’f[h]ilidh eile acht duinn
(f) dlighIDH coir[e] cnáim[h]

The book of an unjust hand [= of a condemned/conquered owner?],
a treasure-trove in its [stories of] Troy and [of the] Táin;
better [were] its pillaging by us!
Not noble is it bestowal
on another poet instead of us:
A bone is meet for a cauldron.