Oh yes good idea ! I'll look at the specs to see if i can gain the missing millimeters.
Honestly i dont think it will be dangerous to weld a small portion of steerer. It's just to get over the axis of the second screw of the stem. Now it's just under. Will see and update the topic.
Better to get a zero stack headset than try welding on a bit of steerer tube.
Something like this.