If you do the wheel rate math, they shocks are well within the boundaries of the valving. Even if you are using factory bars. You will notice a significant loss in roll resistance with a lighter spring and would be the most adverse effect of the car.

and yes, these shocks are stiff enough to hold the suspension in compression and extension to some degree. You can press down on a corner of the car and it will remain compressed for some time until the shock bleeds down. Your phrasing and FWD experience listed is telling. Our spec Celica was the same way. After a session on the track the car would be an inch lower than when it started because of the amount of rebound we had dialed into the dampners. Our shocks aren't that aggressive and unless you are racing a purpose built car, you wouldn't want that valving on the street.