Hi, I've been trying to install a Graco MySize 65 Converible car seat in the rear-facing position in my 2010 Prius, but haven't been able to get it tight enough. Is it possible to install the seat in this way in the Prius? We can get it tight enough if we use the LATCH system on the passenger side, but would prefer a seatbelt installation in the middle for added safety. My daughter is almost 13 months, average height/weight. Thanks for any advice!