How to install RTC 2.0 into Domino Designer 8.5.2

Question from our user community:
I have now a RTC 2.0 project area but how can I install the RTC 2.0 client into the Domino Designer?
When using the RTC 2.0 client install you can add the client to an existing Eclipse IDE which requires the file eclipse.exe in the eclipse installation.
When using the folder ...\framework\rcp\eclipse\plugins\com.ibm.rcp.base_6.2.2.20100729-1241\win32\x86 which contains eclipse.exe in a Domino Designer installation, the install manager raises an error
Installing plugins (like the RTC client) into the Domino Designer needs an eclipse 3.4 update site, a p2 update site do not work because p2 requires eclipse 3.5.
In eclipse 3.4 you can copy new plugins into the plugin folder and after a restart, the plugins are available in eclipse, but in Domino Designer this is not working, an update site is required.
I have now a RTC 2.0 project area but how can I install the RTC 2.0 client into the Domino Designer?
When using the RTC 2.0 client install you can add the client to an existing Eclipse IDE which requires the file eclipse.exe in the eclipse installation.
When using the folder ...\framework\rcp\eclipse\plugins\com.ibm.rcp.base_6.2.2.20100729-1241\win32\x86 which contains eclipse.exe in a Domino Designer installation, the install manager raises an error
Installing plugins (like the RTC client) into the Domino Designer needs an eclipse 3.4 update site, a p2 update site do not work because p2 requires eclipse 3.5.
In eclipse 3.4 you can copy new plugins into the plugin folder and after a restart, the plugins are available in eclipse, but in Domino Designer this is not working, an update site is required.