Stair case shoerail minimum width and extending width of closed stringer
Typical Balusters will tend to make the stringer rotate when a force is applied perpendicular to the stairway. (Code requires a resistance of 200 lbs. applied at the top of the guardrail and perpendicular to the guardrail.) I’d try installing several newel posts along the stairway. They could extend from the floor up to the guardrail height so they won’t rotate.