I felt it was worth resurrecting this old thread on Rise/Drop symbols because the main issue originally discussed is still unresolved: http://www.augi.com/forums/showthread.php?t=100008
I went to fix the Rise/Drop duct symbols in a 2011 Revit MEP project as someone had switch them to the non-filled versions so ups and downs look virtually the same. Supply and Return are an easy fix since we use Cross - Filled and Slash - Filled respectively. Exhaust is the problem child as our standard is to use the Reverse Wye symbol but for the Rise, there is no Reverse Wye - Filled option.
I know the previous discussion wondered down the path of Autodesk providing custom symbol options but I think the original intent is to at least add any other relatively common industry standard symbols. I would think just adding a Wye - Filled and Reverse Wye - Filled would cover 90% of the issues. I am shocked this hasn't been addressed sooner, this is pretty basic and I think just rolling over and saying "Well I guess Revit can't do that" is idiotic for something so basic. Autodesk, don't worry about adding anything fancy, we just want a few more symbol options.