Thumbnail on product list to small when custom field is displayed

-- HikaShop version -- : HikaShop Business 2.6.4
-- Joomla version -- : 3.6.5
-- Browser(s) name and version -- : safari

In the view product/listing_img_desc, I replaced the code for the product description with the text in the custom field.

The thumbnail of the image will than turn smaller than in the products without a text in the custom field.

I am not the best of php-programmer, so please help me to figure this out.... I would like to keep the size the thumbnail/image has, when no custom field is filled. See the attachment.

I tried changing the css, but with no satisfying result.

See the before and after attachments.

I got the image to be bigger. But the font, fontsize and margins of the rest are also changing. That was not my intention