Height of accordion slider

I’ve set up the accordion slider on my home page with 7 images using the “entry with sidebar” setting, captions and links – and it works perfectly. However my client now wants the height of slider to be greatly reduced – by at least half. I’ve trawled the forum and discussion and found the suggestion to edit the php file – which I did – then tested by using the same settings of slider on another page and uploaded resized images but it didn’t work. I’m sure I must be missing something or perhaps there is a better way of doing it. Please can you help. Thanks in advance.