The first 'í' in 'síníonn' should, of course, be long.
is SEEneen shay a more correct pronunciation?
Remember the 's' is slender - SHEEneen.
SHEEneeON? With 3 syllables?
No — the o is there only to show that the nn should be pronounced broad.
Could you say contract instead of document or is there antoher word?