Thanks for posting the images; a brief test shows the converter's image is substantially better than the image shot with no converter and subsequently enlarged to the same size (assuming the converter-less shot was in focus, etc.)
This is the best 100% performance I've seen for a converter (either front or rear, cheap or dear) on the DA 55-300 at 300mm. I had previously tested the Oly 1.7x and Nikon 15ED front TC's. - their performance was not so good as shown here.
Top with canonTC-DC52B, Bottom without TC, enlarged to match,
Thanks for the info,
Dave in Iowa
I'm going to buy one right now.