You could try this:
Please go to Full Parameters and save the parameters to file. Open the file with your favorite text editor and change the parameters.
H_SV1_REV,1 …set to -1 to reverse
H_SV1_TRIM,1500
etc.
Save the file and in Full Parameters load the modified file and write the parameters to Pixhawk.
I think it is messed up because they renamed the parameters from HS… to H_SV…