Hi, I need to buy a booster for a relative. I have a FPSV booster, and when moved out of the car or between cars, the top sometimes comes apart from the bottom. That is not a problem for me, as I know how to put it back together and use it properly. It would be a problem for this relative, though. Can you tell me which boosters are either one piece or are screwed/fastened together so that it doesn't come apart when being moved? I'm considering a Cosco Pronto, Cosco Traveler, Evenflo Big Kid, or compass, so if anyone has any reviews of those specific seats, that would be great, too. This is for a 4 year old, don't know height, she's probably 40 lbs. Please don't suggest a harnessed seat, these relatives will not use one (although I know the advantages, my 4 yr old is in a Nautilus). Currently this child is is NO seat at all, so I think a booster would be better than nothing, and the best chance of getting her into a seat.