The 9600 has a pressure control setup that makes the hydro behave "funny" compared to models which are not set up like it.  Whereas a 7720 would pull until the engine stalled or the relief let go, the 9600 will not.  As pressure rises the hydraulic logic in the hydrostat controls circuits will effectively "back off" the swash plates from  the position demanded by the control handle.  This can, in extreme situations, leave you sitting on a hill in 3rd gear with the control lever ahead and the engine not really pulled down.  

That doesn't really answer your question, but it is a consideration.   Answering the question I think will require some looking at pressures and temperatures to really figure much out.