Only for Sendy 1.1.7.8 and 1.1.8.5:
The mod I had proposed for Sendy 1.1.7.8 (last december ) still works fine in Sendy 1.1.8.5: it allows to select the number of lines displayed in the "Last Opened" reports (instead of the default of 10).
Screenshot (above): http://dl.dropbox.com/u/406945/screenshot-sendy-1.1.8.5-report-hack.png
Download: http://dl.dropbox.com/u/406945/sendy-1.1.8.5-report-hack.zip
To install (Only for Sendy 1.1.7.8 and 1.1.8.5!!!): just replace report.php by this new one in your Sendy installation
Hope it can help!