I'm with bullet08. Gravity is a law. I always obey the law. Not a fan of pipe racks any longer. One too many bumps with an elbow or slippery fingers .......
I wouldn’t be a fan of the pressure being on the stem of the pipe and
being held from the bit ensuring the maximum amount of force on the stem. Might be nothing but it would aggravate me and Id worry about the stem becoming malformed and possibly loose at the tenon as well.