My dad used to have a few Minis, and they were very bouncy. I put this down to being a bit under-damped more than the springs being particularly stiff. It was a 50s family car after all. Something like the UF GTR would obviously be a different story. Also don't forget we have perfect dampers in LFS, which do act reasonably differently to real life dampers (just like those graphs you pm'd me with Tege).
Calling the XF GTi a "hot hatch" by todays standards is a bit much, consider the hatchbacks on sale now. It's still a bit warm, but your average "shopping cart" rolls all over the place, more-so than this GTi setup.
I kept the XR GT softer than the Turbo so that there was some more difference between them, the Turbo does LOOK a lot more like a sports model than the GT so I made it FEEL sportier as well.
Evos/Imprezas probably use Torsen diffs which can have much higher locking values without a negative impact to the handling. Since those diffs aren't available in LFS yet I have to compromise.
The FXO already has the stiffest suspension of the Turbo trio, but I doubt it would have an LSD (considering it's very similar to an Astra Coupe).
My Dad also built a Westfield some years back so I can assure you that setup is reasonably accurate. Once I watched him drive up the road with just him in it, and you could see that the car was lower on the drivers side than on the passengers side (and this was from 30m away). As a basic car it did not have an LSD or anti-roll bars. The LX6 is more like a racier model, so it gets a sportier package. It's already the stiffest setup in the pack. It also has enough diff locking to prevent inside wheelspin (well, just about) - any more than this and you're just making the car oversteer more under power (not something the car needs).
The FZ50 is NOT a Porsche so you can only use the 911 settings as a guide, you can't take them literally. I doubt unsprung masses match for starters (so there's more to think of than you might at first think).