Featured images size at the archive / home pages is 200 x 180 for standard posts.
600 x 440 dimension is advised to satisfy the different image dimensions at different places e.g. Home / Archive Pages, Single Post / Page, Slider Posts etc
You have to change the code at different levels to satisfy your need.
I will not recommend this change due to several reasons like,
– It will over-write in after the update of contango new version which is expected in this month.
– You have to made several changes to meet the Contango responsive layout.