How to reassociate .RPT files with i-net Clear Reports?

OS: Windows 7

1. A long time ago I installed Crystal Reports. This is relevant for later. I need CR for another app.
2. I installed i-net Clear Reports 12.1. Double clicking on an RPT file opened the file in CR 12.1 as it should.
3. This week I installed Clear Reports 13.1. Double clicking on an RPT opened the file in CR 13.1 as it should. But 13.1 is buggy so I uninstalled it.
4. Now when I double click an RPT file it opens in Crystal Reports, not Clear Reports 12.1.
5. How do I reassociate .RPT files with Clear Reports 12.1? There is no menu option for that in the app.

Note:

1. Crystal Reports is not a default program under Control Panel, Default Programs so I can't delete it from there.
2. The command line to start Clear Reports is complex so I can't set the startDesigner.bat file to be a default program. Windows won't let me.
3. When I right click a .RPT file, and choose Open With, I can't add Clear Reports as a program because this process won't work with startDesigner.bat, and the command line is complex, see below. This means most of the web sites I Googled use this method, and they don't work for me.
4. When I right click a .RPT file and choose Properties, then the Change button, again this doesn't work because i-net Clear Reports is not listed as a program here. And clicking Browse for a program also does not work because the command line is complex, the Browse button only selects a .EXE file, you can't do anything else. So one question might be how do I register i-net Clear Reports so the complex command line appears in the Open With dialog?

The RPT files are supposed to be opened by Clear Reports designer, aka i-net Designer 12.1. The command line for it in a short cut is: C:\Windows\SysWOW64\javaw.exe -Xmx2048m -jar "C:\Program Files\i-net Clear Reports/core/Designer.jar". Notice there are no parameters or RPT files passed to this shortcut command.

There is also a batch file startDesigner.bat which takes the RPT file as a parameter. The command line inside the .BAT file is: start javaw -Xmx2048m -jar core/Designer.jar --open %1.

But when I go into Control Panel, and program associates, there is no option to specify a whole command line to start up the program, there is only the option to select a program (i.e. EXE file) to use to open .RPT files.

Thank you!

EDIT: I created a .REG file like it says here, double clicked on the .REG file to install it, and rebooted. That didn't help. .RPT files are still being opened by Crystal Reports.