You can use a licensed ARES Commander to convert the FLX-files to DWG format. Attached is a lisp file that can convert all FLX-files of a folder to DWG-Format.
Note: The 30-days-Trial license of ARES Commander is not supported from the FLX2DWG-LISP command.
Please save the FLX2DWG.LSP-file to your Windows desktop.
Start ARES Commander (Windows Version).
Type _LOADAPPLICATION to the command line or go over the Classic Workspace-->Pulldown menu 'Tools'-->'Load Application...' and select the saved FLX2DWG.LSP file.
Now type FLX2DWG to start the command.
Then you specify in the upcoming dialog the source folder with your FLX-Files.
Also you specify an empty target folder for the DWG output files.
The converted DWG-Files can then be opened in all ARES Trinity Products, DraftSight, CorelCAD und AutoCAD.
Download the FLX2DWG.LSP-file from here.