I skied in a clinic once with Victor Gerdin, who had fallen off a ladder and broken a leg during the summer. To avoid pain from the boot, he was using plantar flexion to pressure the front of the ski.
That's how I ski all the time. I use very little leverage from the shin/tongue. Most of the pressure comes from my feet, as Kneale calls it- plantar flexion. The pressure on my shins \ is mostly for stability rather than leverage. I've discovered that you don't need very much cuff leverage if everything is adjusted properly.
My approach is that I will find the support (fulcrum) point in the middle of my foot and make sure that is well supported under my insole. usually with thin layers of tape and then slightly
pad underneath the fleshy part of my toes (careful not to pad too far forward) so I can gain more leverage from my foot simply by pushing my toes down. I'm sure somehow I extend the ankle too a bit, but I am largely unaware of that. Being limited and having to find alternative ways to approach things can often unveil a better way to ski.
Interestingly... I was just with my nephew yesterday who was lamenting about his boots. I had an hour to kill, so I took apart his boots and started "upgrading" his "custom" insoles. I started with the toe pads. It doesn't take much. I stacked 5 layers of 3M shipping tape and cut it to the right shape. I ultimately doubled that to 10 layers before he could feel a difference. Once that was done, I added a about the same amount of tape at his foot's "fulcrum point" in 1/2" x 12" oval. When I put him back in his boots, even in his living room I could see his stance was entirely different. It was remarkable as he was then able to access the inside and outside edges of his boot with no body movement, only feet and ankles. I won't get to ski with him, but he's off to Aspen next week, so I'm waiting for a full report.