i have a small car and I am a tall guy, but have been able to make this work almost every time i go for it. What I will do is start making out with her. When the kissing starts to get heavier I reach around the side of the seat and pull the lever that puts the seat down. This move is golden. Be smooth about it and support the seat a bit as you let it down, this way it is not too abrupt. It catches her by surpise. The girl laughs every time, she thinks it is fun falling back like that, and there is a feeling like you are catching her. If she asks what you are doing just say you are getting comfortable. If you can pull this move off you are pretty much in it to win it. I will then climb over closer to her and start kissing her neck, i will then climb into the passenger seat with her, and wrap myself around her. I will make a moment of small chat to make this transition seem comfortable for her. I will then make out just a bit more, caressing her body and kissing her neck. Before things ramp up too quickly I will then say I bet there is more room in the back seat. The timing is important because if you wait too long you might as well just escaslate in the front, but too soon and there is no steam from the last transition to the passenger seast. Since the seat is down it makes it easy to just climb right back there dont even need to get out. once we are in the back I quickly put both seats up all the way for more room. I don't bother sliding them forward though, that would take to long, you have to be quick and just get the lever on the side of the seat. At this point I go full steam. Usualy to make this transition I go straight for her breasts and wreslte her shirt off. Rub her pussy through her clothes a bit more then hand down the pants then pants quickly off. ect ect.
To recap
Stage 1: make out driver from seat to seat
Stage 2: Drop passenger seat. This is the golden move. Girls love it, it gives them the sense they are falling and you are catching them. It's adeventure.
Get closer, make out heavier, kiss neck.
Bear in mind, I have an older car so I cannot vouche for this move on an electric seat adjustment.
Stage 3: Clim into passenger seat. Don't ask, just do it. Heavy petting.
Stage 4: Move quickly to the back from the dropped seat. Escalate heavy yet naturley don't jump the gun but don't be to tepid.
Stage 5: Take your car to the mechanic to get your shocks fixed
It is important that you hit each beat right on time. Not too fast not too slow with each stage. During each transition distract her with playful small chat, this makes her feel comfortable and hardly notice the transition. You will find that the escalation windows get closer and closer togther the later the stage. So in stage 1 you will most likely take more time with each escalation but by stage 4 it is one beat after the next. I would say the entire proccess can be any where between 5 to fifteen minutes all depending on the way you two are vibing eachother.
Practice in your driveway some day. Just get really good at quickly droping the seats and climbing in the back and putting the seats up then dropping one and climbing upfront the climb in the back ect ect. Get so good at making a smoth transition and being able to work the seats so quick, she will not even notice you adjusting them. Be so good at this that you can easily lead her from the front to the back.
The easiest way to lead her to the back is to have the passenger seat all the way down. You can literaly step back there. when you are in the back get as close as possible to the passnger lead her past you towards the window behind the driver seat. This is important because it puts you in a postion closer to the seat that is down so you can quickly put it back up while she is getting comfortable in the corner that has the most space before the seat goes up all the way. Once the passenger seat is up all the way you want to put the driver seat up in one motion as you are moving in towards her. She will barley notice you putting the driver seat up because it is in the same motion as you getting heavy with her.
Seat one, seat two, BOOM. In that order.
If you are in a secluded place, take it outside of the car bend her over the side or the hood. Carry a small picnic blankett in the trunk. Lay her down under the stars and let her get a good look at the heavens. The blankett can come in handy on cold winter nights when you are done and just laying in eachothers arms. The front seat is good for her on top. The back seat is good for you on top. Feel free to change postions if you feel it.