Currently there's way to know Avatar Performance Rank before build. However, with some tools optimize avatar on the IVRCSDKPreprocessAvatarCallback, the prebuild performance rank is not actual performance rank. So please let me know actual performance rank on upload window.

Related canny: Request to add hook on calculating pre-building Avatar Performance Rank: https://feedback.vrchat.com/feature-requests/p/sdk-please-provide-hook-on-calculating-pre-building-avatar-performance-rank

P.S. I've made small utility to know actual performance rank. As a workaround, you may use this: https://gist.github.com/anatawa12/a4bb4e2e5d75b4fa5ba42e236aae564d