I asked the question about adjusting KPI to make sure that I wasn't missing something so that I could make some sort of bottom line statement for the average Joe who has read this thread hoping to improve the handling of his car. It is very unlikely that the average Joe is going to fabricate his own uprights and probably won't make new control arms. But, there is a lot he can do to improve his handling and there are things he can avoid that could worsen it.
Wheel Offset - Take the time to look carefully at the effect of the wheel offset not only on brake caliper and control arm clearances, but also on the contact patch location in relation to the swivel axis of the upright (scrub radius.) The exact style of wheel that blows your skirt up may only be available for a particular make/model of car, but the offset that is required by that car may be all wrong for your car. (Today's front wheel drive cars call for wheels with huge offsets, so that may work to your favor. However, be aware that they may actually have too much positive offset to clear controls arms, etc.) As much as you hate it, you may have to look for a close facsimile that comes in 3-piece wheel that allows for an offset that will minimize the scrub radius on you car. A car that looks good but handles like a pig is no fun at all.
Wheel adapters/Pin Drive adapters: Many have fretted over the unsprung weight that adapters add to their cars, but don't consider the increase in scrub radius that they bring. If you just have to use these for the aesthetics - and I must admit that spinners not only look good, they also just look right - consider where they will put the center of you contact patch and try to use wheels whose offset will compensate or even improve the scrub radius.
Big Brake Kits - Big, multipot calipers look really cool! They can obviously increase your braking effectiveness. But, if their size and placement is going to cause you to use wheels with little, or even negative, offsets, those big brakes may be necessary to slow down enough to get you car to handle through the twisty bits.
Bump Steer - in many cases this is something that can be corrected with modifications to existing parts. Bump steer has received a lot of attention in recent years. As a result, it is far better understood by much broader spectrum of mechanics and shops. The diagram below from an article by Longacre Racing Products on
Racer Parts Wholesale’s website shows in the simplest terms where the tie rod ends should fall and the line segment on which the tie rod should lie. Bump Steer kits/modifications will get the tie rod to fit the requirements shown (as much as possible anyway.)
Alignment settings – in most cases, the alignment specs provided by the manufacturer of your car represent a best compromise between good street manners and performance handling. Without the fabricating new suspension parts, it is not likely that you will be able to make huge changes in these settings. That is not to say that there is not room for tweaks and changes for personal preferences or specific uses of the car: a continuum from race track use through highway only cruising. There are a few things to keep in mind though. As much as humanly possible, make changes to one setting at a time. Make changes a little at a time. Be aware that, for all intents and purposes, changes are not made in a vacuum: a change to any one setting will likely change other settings, so always recheck all settings when ever a change is made to any one value. Write down everything you do in great detail. Not only will this help you to understand the cause-effect relationship of the various tweaks that you do, but also it could help you get back to where you started if things really get hosed.
If in the end sorting what you have just isn’t satisfying, reread this thread to consider that kinds of things that will have to be changed and how they will have to be changed to further improve your handling. One must always keep in mind that handling is a highly subjective thing, but, as we said in the US Navy, the guys contributing to this thread “have their shit in one ditty bag.”