1kloc is a bit abstract ; it seems you are in a great position to give a true bundled weight ; preact is about 3kb which is my fav for years - good job for the effort and results !

9kb (minifier+brotli)

We could remove 3kb by removing the router but that's not gonna happen. You're more than welcome to minify+brotli it yourself if you use vertex.js in production.