Enable "Disable Expressions evaluation" checkbox and it will significantly improve opening up report with Jasper Studio 7.1.
(This new security preference is not in Jasper Studio 6.2.)
Go to Jasper Studio 7.1 menu bar->window->Preferences->Global Settings->Jasper Studio->Disable Expressions evaluation
<Please see attached file for image>
Other concerns for performance:
The default ram allocation in Jasper Studio 7.2 may be small.
To increase ram allocation, edit "Jaspersoft Studio Professional.ini" and try to up the ram allocation like as below.