I’m well aware of how fractions work thanks Peter. 🙂
What catastrophe do you think will happen with only 20mm clamping surface and 15mm free at the top,?
And do you realise some BMX stems have as little as 22mm stack/clamping surface?
The stem won’t hold, the steerer with quite so much force, which may cause loosening of the headset adjustment.
If you’re really worried, run a headlock