I tried the next stanza.
airdrig Do cosnam temra
cen tairbirt re slúag n-emna
ind rárbúi gargda i n-airbert iarmad arba Cormac
Coro-bris .iiii. catha cona forna fáta finda
i n-enlo cono na._aít croda crinda
n-airdric. rar Do chosnom temra
cen tairbert re sluag n-emna
bui garga i-nairbert iarmad arba Cormac
Coro-bris .iiii. catha conna forsna flatha finda
i n-aenlo conona imchath chrodha chrinda.
The sense of this is elusive right now - as is the metrical form of it. I translate what I can:
To contend for the High-kingship of Tara
without subduing the host of Emain
______ fierce in heroic-deed after which Cormac dies (???)
so that four battles broke ____ upon the ______
in one day _____ _____ bloody Crinna.
I took 'iarmad arba' as "iarmo/iarma" (adverbial 'afterwards) + -d- (infixed 3rd person pronoun activing as a relative particle in Middle Irish. This bit is really dodgy) + -arba 'dies' (in DIL, cross referenced with at-baill)
Otherwise, I'm sure I've made many mistakes.