Discretionary application – 5 year condition not met

Dear Sirs

I am on ILR since feb-13 and due to health and family reasons (father had cancer) I was out of the country for around 8 months. I came back last year and my last 12 months absences within 90 day threshold however my 5 year absence are more than 480.
And 7 year absences are less than 550. I am here since 2007 on hsmp+tier1+ilr.
Can you please advise me whether I can apply for the citizenship on discretionary basis and what are the my chances of success.
I would appreciate if anyone can provide me with the discretionary covering letter template.
I am meeting all other condition as I’ve my home here no criminal convictions and meeting English language requirement and all other good character req. as well.

Regards