Please: help needed for www.sportinjurymatt.co.uk

I have just updated my Soledad theme version and all the featured thumbnails on my 'Featured Categories Style 1 with Magazine Layout' homepage have changed from the 600 x 242 landscape settings I had previously to practically square.

I have tried modifying all the box sizes in Settings/Media followed by regenerate thumbnails but I cannot recall which one changes my magazine boxes or how I managed to change the shape of them 2 years ago.

Please help a.s.a.p as a my 640x242 featured images are only partially showing. Thanks in advance!

Matt

What are they at the moment? What are they called in Regen Thumbnails? 

I still want the box for the first post to be  bigger then the next five, as per the grid lay out, but the proportional dimensions of both need to be such that the whole content of the 600 x 242 shows.Hope that makes sense? 

Will that restore the layout to like it is in the attached screenshot? 

Do I need to clear cache after Regen Thumbnails for it to show up? 

Awesome. Thank you for your help. After clearing cache it worked. Many thanks!