You can use ARES Commander 2018 during the 30 days trial period 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.
1) Please save theFLX2DWG.LSP-file to your Windows desktop
2) Start ARES Commander 2018 (Windows Version)
3) Type _LOADAPPLICATION to the command line or go over the Classic Workspace-->Pulldown menu 'Tools'-->'Load Application...' and select the save FLX2DWG.LSP file.
4) Now type FLX2DWG to start the command
5) Then you specify in the upcoming dialog the source folder with your FLX-Files
6) Also you specify an empty target folder for the DWG output files.
The converted DWG-Files can then be opened in DraftSight.