Sorry the tutorial left you wanting more. I will try to improve it. Flipper discs are awful and I will try to help you get rid of the ones you have. I have converted at least 6 or 8 to DLs with no problem.
Merge is very demanding of system resources, so I suggest you close or disable any background stuff that may be running on your PC and disconnect from the internet. If you need to refer to this post, copy and paste it into Notepad and print it out.
Insert the disc you want to convert into your drive with side B down and set to be read. Open DVDFab Platinum and make sure the drive with the movie has appeared in the Source window. Select Customize mode with the NO MENUS button selected (you can use Main Movie but it sometimes selects the wrong title on side B of flippers). Use the preview window to make sure you have part 2 of the movie as the selected title, then stop preview and make any selections of audio tracks and subtitles. Remember what you have selected here as the merged titles seem to run better if both are the same as far as audio tracks are concerned. Now select a hard drive folder as the target and click Start. Click Finish when done.
When Step 1 completes, take out the disc and flip it one last time:) so that side A is down and let it load into DVDFab Platinum. When the analysis completes, click Merge and make sure the disc shows up in the Source window. Now select the title for Part 1 of the movie and verify you have it right with the preview window. Select the audio and subtitle elements that match your choices from Step 1 and press Next. Verify that the first and only item on this screen's Title List has the little DVD icon and possibly the title of the movie (may say just DVD_VOLUME). Now, while still on this screen, click on the Source folder icon and open the VIDEO_TS folder of the hdd files of Part 2 of the movie that you prepared in Step 1. The screen will snap back to the first Merge page to allow you to double check all settings (which should be fine since you made these choices in Step 1). Click Next and verify that the second item on the Title list has a folder icon and the correct running time for Part 2. It will probably just say DVD_VOLUME beside the folder.
While on the second Merge page, select the Target drive and make any changes to burn speed, etc. in Common Settings if needed. (You can also write this to a folder on the HDD if you want to verify it by playing before burning.) When all is setup and ready, click Start and the Merge process will begin. If something goes wrong during the process, click the SAVE button before exiting to write a log file.
Post back if you still have problems.