With Eclipse Luna M6 and M7 we introduced the possibility to set the stylebits for user interface controls via persisted state data. Use “styleOverride” as key and the integer value for the SWT stylebits you want to use.
For example to create a SWT shell which cannot be resized you need to supply the integer value for SWT.SHELL_TRIM & (~SWT.RESIZE), which is 1024 on the MWindow application element.
If your MPartStack should render its tab below the parts, use 1024.
This results in the following application (in which the window cannot be resized).