We used to stuff our car seat in the back of a eagle talon
and in the back seat of my 74 bronco
Using a ratchet strap
And when we took the top off in the summer we had a leather helmet and goggles like the old bi plane pilots wore
He loved it !
The easiest thing is to just buy a seat and dedicate it to the car
It's not too bad stuffing the kid in
But moving the seat all the time is a pain
The panemara Porsche isn't too pricey when you consider you could use it for a daily driver and not be making payments and ins on two cars