Welcome aboard. I'll be honest and say I don't 100% know the answer to your question but I think sewing things on will could change the way the sail performs relative to how it was designed. AFAIK
, sailmakers spend time engineering their sails to work in a specific way whether it's for racing or cruising or just daysailing durability.
I think that sewing something in may alter the sail and may reduce it's effectiveness and durability racing or not. Others may have other opinions