Hi,
From an end-user perspective when using the Path Reinforcement command, dimensions like A and E is not accessible(out grayed) in the project document.
So most likely trying to do this programmatically is also not possible.
However, each RebarShape has it's own rfa.file(family); you should try open the rfa.file and edit the family(change dimensions like A and E).
Use the Revit Lookup tool to examine which values you are interested in if you want to adjust it programmatically.
Once you have changed the dimensions you can reload the family to the project document to see the adjustments you have made.
Once a Path Reinforcement is created in the document, you should be able to change its RebarShape(Layers 'Primary Bar - Shape')
This might be interesting if each RebarShape has it's own set of values so you can replace each Path Reinforcements Shape whenever neccessary.
I hope this will point you to the right direction or is useful information for you.
