I did some measurements and calculations today as i was tuning the forward lean in my boots. I am posting these to save others the trouble. I am measuring the angle of the shin bone (front of the tibia) to the floor with mild pressure on the tongue.
boot forward lean:
for typical hinged cuff boots, wedging or screw type adjustments between the rear of the cuff and the lower part of the boot give about 5 degrees forward lean for every 8mm of shimming, assuming 100mm radius from the axis of the hinge to the shim.
measuring from the angle of the shin to the bottom of the boot sole, the part that contacts the bindings, my Dalbello Krypton cross boots are 22 degrees forward lean. With the largest 8mm shim, which is 100mm from the pivot point, they increase 5 deg to 27 Degrees. inner sole has no effect on this, no matter the ramp of the internal footboard of the boot.
For every 10 mm increase in heel height with external heel shims taped to the bottom of the boot, there is a 5 deg increase in forward lean on 310 mm boot soles. figuring 250 mm from the heel to the front of the friction pad.
I have 5 deg that i can add or subtract with a custom made shim that fits between the boot and the screw in rubber walking pad for the heel of the boot that gives me another 2.5 deg when i want it, for max of almost 30 deg forward lean.
There is much more adjustment possible by wedging the heel than by external shimming, but it also limits the range of motion possible flexing the boot. This may be more than counteracted by greater leverage with body weight on a heavily forward tilted tongue.
The inherent inclination of a boot design can not be radically altered by external shims without risking binding malfunction. If there is not provision in the boot design for adjusting forward lean, you can only fine tune but can't turn a pussycat boot into a charging tiger.
FWIW, my idiosyncratic preferences, which seem radically different from what I have read from posts by others, are as follows:
30 deg total shin inclination feels best for carving without having to bend at the waist and with knees bent where i like them for speed and challenging snow or terrain. At this lean I can freely touch my toes or stand up to mildly bent knees and still stay balanced over the sweet spot. my ability to tip my boots on egde with my knees is greatest at this angle. more or less diminishes angles. I can flex the boots forward more but i feel like even more stiffness would be good at this level of aggressive forward tilt.
At 27 degrees I can still carve but I need a touch more bend at the waist than I like to keep the sweet spot, and I can touch my toes and keep weight on the sweet spot just behind the ball of my foot with effort. I can flex my stiff boots comfortably without falling forward. This would be nice for racing I think, because racers tend to bend more and stay lower with their shoulders than free skiers who opt for more comfort. I can run gates at this setting if I focus on bending mildly in the direction of a tucked stance. At my age and slightly limited flexibility I have not been able to find a way to carve tight fast turns with any less lean than this.
At 22 degrees forward lean. I am most relaxed standing around on my skis, but I have to ski with a very bent back and waist to stay over the sweet carving spot of the ski, it is more work to keep from being thrown back on the tails. it is also very hard to flex my boots because i have no leverage as I push forward on the tongue.