Glad you find it working for you, SSG. If it really does (and it well may), that means that you are one who needs it.
The photographs you linked to are interesting. First, inside tip lead is clearly evident in every single photograph, although it may be somewhat hard to see in those photos where the skiers come directly toward the camera. And second, most of these skiers have rotated their upper bodies significantly into the turn in these photographs--note the inside hands and often shoulders pulled back. This is not an uncommon situational move in racing, but it is not a fundamentally optimal stance in general. And if anything, it tends to reduce inside tip lead as it pulls the outside half of the body forward and squares up the pelvis. So any tip lead here at all is significant!
Be careful about reading too much into any video, photograph or photosequence of one particular turn, even when looking at several racers in the same turn. Many movements of great skiers are situational, not fundamental or generally "correct"--great skiers have tons of skill and break the "rules" freely, whenever needed! If you had images of the whole run, you could easily find photographs of these same skiers in very different positions in other turns--often with much more tip lead.
In any case, clearly some tip lead "happens" in most good turns, as these images show. We MUST give ourselves permission for that, or else we inhibit some critically important movements.
You are right that excessive lead is always a problem--as is excessive anything. I would assume that that goes without saying!
It is worth noting too that "parallel shins" does not necessarily imply anything about tip lead. Nor do many of these skiers exhibit parallel shins in these photographs (Hosp and Schild of the women, and Benni Raich of the men, come closest.)
To return to my car analogy, if you were to turn the wheels of the car as far to the right as possible--all the way to the stops--there would be considerable "tip" (right wheel) lead. But how often do you do that in "normal" driving on gently curved roads? Generally, we only need to turn the wheels a small amount to steer most turns in cars, although very tight maneuvering involves a lot more turning of the steering wheel. Same with skiing--the amount of tip lead reflects the intensity of the leg rotation, which reflects the tightness of the turn radius. Rarely do we rotate our legs 90 degrees from straight ahead, but that is what happens in the exercise known as "pivot slips" (seen in the animations in the thread CGeib linked to above). Pivot Slips involve exaggerated rotary movements of the legs, resulting in more tip lead than most (but not all) turns. The Basic Parallel Turns that I demonstrate are quite short radius and very complete (meaning that I needed to turn my legs quite actively), but far from as extreme as the Pivot Slips, so tip lead is more subtle. My fairly narrow stance also results in less tip lead than a wider stance would produce.
Understand the things that affect tip lead--leg rotation (varies from turn to turn), differential leg flexing (results from inclination into turns and/or from skiing across the slope), upper body discipline (rotation into the turn tends to square things up; "countering" away from the turn tends to increase lead), stance width (the wider, the more tip lead from the above causes), and fore-aft movements of the feet (ie. pulling the inside foot back or pushing it forward).
With this understanding of the many variables involved, it is as over-simplified to say it should be "a couple inches" (or any other arbitrary description) as to say "the optimal edge angle in turns is 45 degrees." Neither of these would be advice I'd want to implement!