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Style templates are not supported (.jrtx) as this file would need to already exist on the server for the report to be created. It can't be pre-compiled into the jrxml.
Report Pagination
Don't use report-level pagination flag. It appears to slow down PDF display way down and doesn't seem to change anything.
Excel/CSV Export
The design of your report heavily influences how the report will be exported to Excel format (XLS). Things to consider:
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