I experienced a huge FPS drop with both the Classic and the Professional version of the MD-80 in Prepar3D, a few days ago. But the problem seemed to get fixed after deleting the Prepar3D CFG file and let it rebuild itself (I was so stupid to make a shortcut to my previous CFG which I deleted, so I couldn't restore it). I just wanted to report this in case of any other BETA tester would stumble upon this issue. I will also post this in the Super 80 Professional forum.
/Viggo