I'm really not a fan of cantilevered loads anchored to the stems face plate bolts.
A cantilever is attached at only one end. The weight hangs at the other end and the load causes the structure to act as a lever against the anchor point.
Stem face plates are designed to provide clamping force in line with the stem. They are not designed to support bending loads which actually pull the bolts at an angle to the stem.
I'm sure some heavier stems support the load just fine but am simply encouraging people to be careful and consider what they are asking their stem to do vs what it was actually designed to do. Some stems are extremely light and I'd hate for a cracked stem or face plate to take someone out.
-Tim-