Hi. In the type properties of the dimensions, change the units to feet and fractional inches and choose the appropriate rounding. Remember you can also override dimensions if you don't need to create a new type.
If this solves your problem, Please accept as solution.
Structural Design Engineer
MZ & Partners Engineering Consultancy
Stacked Fractions are not possible in any of the Revit flavors.............It's been asked for as long as I can remember (2007)
Virtual World Designs
VDC & BIM Model Design, Clash & Coordination
Building Design Suite Ultimate 2013
Charlotte/Gastonia, NC & Jacksonville, Fl.