I think I have made a similar adjustment. I took the arm pads off (remove teh cushion and unscrew the bolt). That leaves the bracket/arm thingy that connects the armrest to the base. Unscrew the other end from the base (I think the hole may actually be in the inverted-U bracket that holds the arm extenders....this is from memory). Now, put the arm rest back on the base directly (into the hole in the inverted-U bracket if that was the original hole)- using the same bolt that originally held the armrest to the bracket/arm thingy.

One thing - this places your arms in a more narrow position, so be sure you are comfortable with it.

Alan