If you receive a message like this from Google AMP Validator …
“The author stylesheet specified in tag ‘style amp-custom’ is too long – document contains 50154 bytes whereas the limit is 50000 bytes.”
… then this is because a maximum of 50 kilobytes of individual CSS is currently allowed on an AMP page. For more information about this policy, please see the documentation page “Style and layout errors” of the AMP project.
Reduce the size of the custom stylesheet used on this page to be under 50 Kilobytes.
ASA2 can’t do that automatically. The more different templates you use on one page, the more CSS has to be loaded. Reduce the number of different ASA2 templates on one page to not exceed the 50 kilobyte maximum.