My shin hurt and soft tissue surrounding the bone swelled every time after a day of skiing.
The hurting spot was located exactly where the edge of upper buckle is.
I realized that the problem was caused by the buckle.
Upper buckle is a point that restricts shin movement when it moves forward.
Because the boot tongue outer shell is not stiff enough to spread the force evenly, the force is applied to the shin almost at one point, i.e. where the upper buckle is located.
First, I attached some hard (made of aluminum) pads to the boot tongue outer shell to spread the forces evenly and I placed soft pads between the shin and tongue.
It worked, but later I found a better solution.
I loosed completely upper buckle and tightened power straps as much as possible.
To tighten power straps, I tightened upper buckle first as much as possible.
Next, I tightened power straps and I released completely upper buckle.
So, the power strap is tightened as much as possible, upper buckle is released and lower one is tightened to provide a boot good fit.
It works very well.
I don’t have any problems with my shin any more.
Power strap is flexible and obviously much softer that aluminum buckle, so the contact force is spread more evenly by boots tongue shell.
Besides of that, the strap is located higher where the bone is thicker and stronger so a shin can endure the stress better.
So, don’t use upper buckle. Use power strap instead.
Ski boots can be design beter to prevent shin problems.
Relatively flexible straps and the buckles that are used only to tighten the straps could do it.
Also, tongue outer shell should be stiffer to spread forces evenly.
Many years ago, rear entry boots were quite popular.
One of their advantages was that they were easy on shin.
Some boots can cause the shin problems because boot shell is not properly design..
Couple of years ago I tried some boots, probably Nordica as far as I remember.
Every time I bent my legs and moved shin forward, the front part of boot upper shell was bending to “C” shape applying pressure to my shin (middle of the“C“ touching the shin).