Not sure what you’re asking, did I test what? I’m having no issues with stacks that came from high Sierra. Stacks for most users running Mojave aren’t having problems.
This is from YourHeads FAQ page
Since you have installed the latest RapidWeaver you can also download and install the latest version of stacks (the plugin not the 3rd party stacks) if you haven’t yet. If that doesn’t work then contact YourHead support with the information requested in the FAQ.