My sv27 has the same crack and so does my mates. Its obviously a week spot on these boats.
On mine its just through the gelcoat but its right through on my mates, i have read of other sv27
owners having this crack appear aswell.
There is a mold line that runs across the back right where the crack is if you look closely.
I have decided not to do anything with mine unless it gets worse, but i know what you mean
when you say it bugs you it does me to but atleast you know its not just yours.