I just finished my name change...well the name change part that was yesterday today I start the process of changing all my banks, and work and insurance over to the new name. I realized about two months ago when I started it that I would need to sign a new name, I downloaded some writing samples. those letters we all learned in grade school and practiced every now and again. plus I signed it anywhere that was not a legal issue.
In your case you could practice or you could sign something shortened, I know tons of people who's signatures are not even remotely similar to there names. I had a teacher in school who's signature was a swirly circle I have a friend who writes the first letter or two then just a squiggly line.
one option you might consider is seeing if you can get people to call you Steffie instead of Stevie its similar and also easily explainable as a shortened version of Stephanie. but really long story short as long as your signature is vaugly like your name and consistantly signed your usually good.