Ball Joint cotter pin

[jacob1806]

Hello, I have a 2008 buick lacrosse cxl, I am doing the lower control arms for the vehicle. on the left side i was able to get the castle nut down enough to slide the cotter pin, however on the right side i cant. If you have done this job you know the clearence is really bad due to the nut being under the cv axle. So with a 19mm open end wrench i have tried my absolute hardest to tighten it, the castle nut is rounded a little bit but i can still get friction. any help???