Has anyone been able to 2 use 2 "free weekend" rental certs on the same reservation without returing the car in middle of rental period?

Either use one coupon for Thr-Fri and another for Sat-Sun? (4 total days)

Or

use one coupon for one weekend (Sun-Mon), pay for Tue-Wed and use another coupon for Thr-Fr? (6 total days)

I think you can only use one coupon before returning the vehicle, but I am curious if anyone was able to combine multiple coupons somehow.

Thanks.