Summary block - can I keep 3 columns across different screen sizes?

I'd like to display 3 columns of images on my page on desktop using a summary block grid, and am happy for mobile to display one column. However, I'm foxed by how it's displaying in different windows.

If i set up a 3x2 summary grid for narrower browser windows, then on wider ones it comes up as 5 across + 1 image on the next row, and a 3/1 grid only covers 3/5 of the row, which both look awful. If I set up for wider screens by adjusting the image minimum width, on a narrower screen the 3x2 reformats to 2x3 (which is fine) but a 3x1 grid shows as 2 + 1 which again looks daft.

Is there a way to make the summary block grid more responsive?

Thanks in advance

I'd like to have 2 columns on summary blocks. 

We have it now in  Lazy Summaries https://www.squarewebsites.org/products/lazy-summaries