Does someone know if there is a company somewhere that are making a négative direct mount stem for boxxer or at least a stem that will make the bottom of the handlebar at the same height of the top of the crown ??
The reason you don't see any stems that are lower is because they would be very long so that they could clear the crown. Why do you want a stem so low anyways? if you ride a low-rise bar or even a flat bar, you can achieve the same result, you can also slam the top crown right on the top of the headset, and make sure that your fork legs aren't extended further in the crowns than they need to be.