I wouldn't have tried to "Grandbag" the classifier early on and get classified as a Sharpshooter in SSP before I was really ready, only to come in DFL in SSP SS at my first several majors.
If you're thinking about shooting a major go ahead and DO IT! They're lots of fun and you'll meet lots of great folks, and the more majors you shoot the better you'll get at shooting majors.
I'm sort of in the same bag. I looked at the classifier and what I knew my skill set to be and was not satisfied with classifying at anything less than EX in SSP. I then classified with my SSP legal gun in ESP as an SS. Depending upon the day, I'm either a so so EX or a very good SS.