No problems fitting car seats in the back of mine; in fact here's a photo of one of them in the BRZ the regional sales guy brought to the dealership back in April of last year. I had this behind the driver seat and a backless booster behind the passenger seat. Worked fine although I did need to move the seat farther forward when my daughter was in the harness seat.
I recently moved my son (8 years old) to the front seat and my daughter (4) into a booster w/back behind the passenger seat and that works great. Both enjoy riding in the car very much! One time I did have my wife in the passenger seat and my son without a child seat sitting behind me and it worked well; his feet tucked nicely below my seat so I only needed to lose a notch or two on the seat rails. The booster is a basic Simpson Racing one (just a basic cheapie with Simpson licensing.)
