calculate "dispersion index" (betadisper, vegan)

hi all

I would like to  calculate a dispersion index or similar from the 
results of the vegan function betadisper.
i would like to know if there is a possibility to e.g. calculate the 
volume of the community dispersion(area of the hull in the PCoA) from 
the betadisper results.
common is to show the distance to the centroid.but I have the impression 
the dispersion within communities are not that clear,especially if you 
have similar variance.
The program primer v5 calculates a disperion index based on  the 
similarity percentage.
similarity percentage is not an option since it is mainly based on most 
counted species.

ideas and help are very much appreciated
cheers natalie