While the RideSafer vest is designed as a stand-alone child restraint, the RideSafer manufacturer has the Delighter Booster which has been crash tested with the current and previous model RideSafer vests.
Technically, using the RideSafer with another manufacturer’s booster seat would be using both products outside of their respective manufacturer’s specifications because they were not crash tested together.
That being said, the Delighter doesn’t have an inherently different design than most backless boosters on the market. Just know you would be taking on the liability of using both together if something should happen.
The RideSafer manufacturer definitely recommends against using the RideSafer with a BubbleBum or a miFold travel booster as they both have their own seat belt guides which may not work cohesively with the seat belt guides on the RideSafer.
