How can i get the slideshow gallery to display images at a certain height?

Hello! 

I'm trying to get the slideshow gallery block to display the portrait images that fit within the screen or a certain size (ie 50% or 70%) instead of displaying them full height / width because it's too long and extends beyond the screen. 

When I mix portrait and landscape images in the gallery, it seems the portrait ones will get cut off. I've added spacer blocks to the left and right of the slideshow block to adjust the width of the gallery block - I'm not sure if this is the best way to tackle it. 

Currently using Carson for my theme. my portrait image size is 1000 x 1500px and landscape is 2551 x 1500px

The screenshots include kinda has one gallery too small and the other too big.

1. How can i get the portrait images to display correctly without being cut off when landscape images are in the same gallery?

2. If I were only using portrait images, how can I make the gallery display the image within my screen - even though I've uploaded a larger sized file?

PS: the site is not live yet, I'm hoping to fix it so I can go live - https://plum-aqua-pyrf.squarespace.com/, password: 123

Many thanks!

Noel

is there something that i can do?