Raising the pension default above the auto-enrolment minimum: did opt-outs rise?

UK food manufacturer, 2,900 employees, around two thirds on shift in production. We are at the statutory minimum for auto-enrolment, 5% employee and 3% employer, and 71% of members have never moved from it.

We have approval to raise the employer contribution to 5%. The debate is whether to raise the employee default as well, to 6%, so the total reaches 11%, or leave the employee side alone to protect take-home pay for people who are already stretched.

Has anyone raised the employee default for an existing lower-paid population, and what happened to opt-out rates? Ours is currently 7%.