Can I use aftermarket accessories or parts with this car seat?

No, you should not use accessories or parts other than those provided by Graco, except for a thin towel or mat to protect your vehicle seat or a rolled up cloth. Using non-approved parts or accessories may compromise the safety and effectiveness of the car seat.

From the official Graco 4Ever DLX 4-in-1 Car Seat manual, page 2

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