"there were no big noticeable differences"
the image plane current is still present on the mast and the outer shield of the feedline, doesn't belong there. it needs to be forced back up into the radial system before you will begin to notice any real improvement in performance.
I have a choke just under the feed point at the base of the antenna. The GPK is mounted as required. I have good swr 1:2:1 / !:3:1.
What need I do more to properly force the current back up into the radial system?
My question is not a challenge. I'd really like to know if there is someting I'm missing...