Displacement field invertion and mean operation

Hi all,

I have some questions about the inverse of transformations and the application of mathematical operations on them.
I am recently working with a time series of volumes that, first, I have transformed into a sequence (Sequence module) and then registered using the SequenceRegistration module obtaining the corresponding Displacement Fields and OutputTransforms. Having these transforms that map the fixed volume to the moving ones, is there a way to calculate their time average internally in Slicer?

Also, what might be the most efficient way to calculate the inverse of each of these transforms?
Thanks a lot!