Split Letter Monograms

Has anyone ever done anything with Letter Monograms?

I have a split letter monogram and in the middle of the letter I want them to put their last name. 

Is there anyway to automatically adjust the text so it is centered and fits inside the split letter?

I see there is a shopify app called product personalizer and that seems to work well but it is only on shopify. 

Any help/suggestions are appreciated.