I see...
I didn't analyze deeper how you use child templates or assets, because it is not so important to optimize here if the chrome takes the most of the time anyway.
1000 pages are so much that optimizing somewhere else than in the output html is probably irrelevant.
We have now in backlog task that could eventually give you a way how to speed the chrome printing.
https://github.com/jsreport/jsreport/issues/490#issuecomment-471622799
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