DS is doing great in his Parkway SGL but I have noticed that he likes to prop up his legs. The base of the seat doesn't come all the way to the edge of the vehicle seat so there is a little ledge. Lately he has been putting his feet up on the vehicle seat when he is sitting there because he says it's more comfy. Is this ok or do they have to have their legs bent in a normal seating position when in a booster?