How do you adjust the image gallery block's carousel transition speed?

Hi there,
I'm using a gallery block with "carousel" on (Squarespace 7.0 - Marta) and would like to slow down the speed of the transition.

I found this solution for the "slideshow" option but have been unable to script monkey it to work for "carousel" option.

.slide {
   visibility: visible !important;
   -webkit-transition: opacity 3s ease-in-out;
   -moz-transition: opacity 3s ease-in-out;
   -o-transition: opacity 3s ease-in-out;
   transition: opacity 3s ease-in-out;
}

Thank you so much in advance!

C

Can you link the site?