I have 2 seats in mine:
This one I can put in and remove in 30 seconds:
https://www.britax.com.au/car-seats/...d-hi-liner-sg/
This one stays in:
https://www.britax.com.au/car-seats/...nd-maxi-guard/
The Maxi Guard is quite a bit seat and I can raise the height up to the roof and it fits a 9 year old in it with room to spare..
Front seats are in normal position for 5'8" driver...