Hey @kris, the simulator and page builder should be smart enough to know the height of the slice, even when smaller than 100vh.
Here is a screenshot of it working using the Prismic multi-page starter:
I believe height detection was added to the simulator within the last year. Could you ensure you are using the latest versions of the @slicemachine/* packages?
In case your project is using the deprecated @prismicio/slice-simulator-react package, check out this migration guide: @prismicio/slice-simulator-react Deprecation Guide - Documentation - Prismic