http://pinterest.com/pin/231653974554896777/
Is that the same layout you're starting with?
3 hearts across and 4 hearts down?
Without seeing the actual pattern, and just going from the photo and your measurements, I'm guessing that each heart area is approx 20"x25".
If you add two more rows of hearts and 2 more columns, you'll end up with something around 120"x125"
If you only add one row and one column, it would be approx 100"x100".
Those measurements are without borders, and without splitting up the hearts (which I think would look weird).
Your desired size is right in the middle.
Was the 112" quilt size meant to be with or without borders?
How wide were you planning for the borders?
Can you use the larger size (6x4 hearts) without borders?
(and welcome to the board)