Less than six months after we moved here, I sat in the Spider with a screwdriver in my pocket and did what you see in the first picture. For whatever reason, the split didn't migrate all that much in the next seven years, but it was still getting wider. What to do? Turn the manic skilled at stitching things up (aka Ellen) loose on it. A half hour later, and voila! If you're not looking for it, the repair is nearly invisible.
We could just re-cover it, but the seats got redone by the previous owner and whoever did the job used high quality vinyl and the fit is just wonderful. The dratted things still smell new. I would've likely had to redo both seats if I wanted to get an acceptable result. Now I don't have to worry about the tear spreading.