making carseats fit so they don't budge

I've found a way to do it and if it's not right, feel free to let me know.
I recline the passenger seat a bit, hook the carseat in via the latch. I
hook it in as tight as I can. Then, I pull the passenger seat back up as
far as it will go. The carseat is in tight, won't budge even a centimeter.
To get the seat out, I have to recline the passenger seat before unhooking
or it will be impossible.

-L....

You are not putting the carseat in the front passenger seat, are you?

toypup...

No, in the middle row of the minivan.

-L....

Oh, ok - I couldn't figure out why the passenger seat affected how the
baby seat fit in. I do something similar but I also have to lean with
a knee into the seat and wrench it down with the strap. It doesn't go
anywhere after that. Try leaning all your weight into the seat with
your knee. if there is any slack in the straps, it's not tight enough.

toypup...

I do the knee bit, too, then I pull the passenger seat more upright. It's
so tight, it's like a part of the seat -- cemented in. People are usually
in awe when they try to move it or get it out. They always ask how I did
it.