So, my friend has a 2006 Scion xB and regularly transports my kids. DS 6, 52 pounds, 48 inches tall in a Graco Turbo booster and DD 2.5, 26 pounds, and 36 inches in a Scenera RFing. Is there any way to get a 2nd booster in the back seat since somethings he would like to transport one of DS's friends? I have a True Fit, a Roundabout50, and a First Years Booster that could be used. I tried to Graco booster and the Scerena and could not them to fit in the back.