You can also define Solo in Playing Techniques, which would allow you to incorporate an extension line if you wished. I prefer to end a solo passage with ord. or nat., but if you prefer a line…
This would be beneficial if there were prolonged passages of back and forth with solo/tutti changing every 5 8ths or something fast, but not very straightforward. In your case a simple solo/tutti without the line would be better, even so when there is already a line present. Two lines are starting to compete with actual staff lines and music becomes harder to read.