I made up a very inexpensive clamp to hold the fixed cup tool in place. I bought a 4" long 5/8" bolt, a matching nut and two large diameter washers.

1. Remove the adjustable cup, spindle and bearings. Then thread the adjustable cup back in several turns.
2. Place one washer on the bolt and feed the bolt through the adjustable cup until it sticks out of the fixed cup.
3. Place the fixed cup wrench over the cup, add the second washer over the bolt end and thread on the nut snugly. You now have the wrench on the cup and sandwiched between the frame and the washer so it can't slip.
4. Use huge force, or even a mallet, on the wrench to get the cup broken loose.
5. As soon as it rotates even a little, begin to back off the nut. When it turns freely, remove the bolt, etc. and remove the cup completely.
6. Use the clamp to hold the wrench in place for final installation torqueing too.