Nice post. I solved the issue by centering the important stuff in the image and then testing on both iPad and mobile until I got it right.
Does your solution also remove the whitespace behind the image (over and under), so it looks correct?
You need to fix your G+ sharing button in the end of the post, Piet. I tried to use it and add a comment before sharing, but it goes away when I try to write something, and the share button dissapears too.