Use MSI Afterburner to record.
Recording performance is based a lot on drive speed. The best possible method is to play the game on one drive and record onto another one. If you can buy a USB 3.0 external drive you should be fine when recording B02.
The FPS drop could also be FRAPS writing two different videos, fraps records seperate 3.9GB files. That's why I use MSI Afterburner to record because it offers better usability and options.