Dennis King wrote:

>>> slân cê[i]ll do chinid (sic) Cormaic
>>> slân cêill do chuin Cormaic

>my first thought is that 
> "chuin" is actually "chum", thus:
> dochum Cormaic = to Cormac

I think, though, that the reading in BB points to an ending -'nn' 
(realised as -'nd') in an exemplar.

If it wasn't for the hair-strokes, BB looks quite a bit more like 
'chund' than 'chinid' - and 'chund' gives the correct syllable count.