Droptines - Yep, 6 fps.
I shoot a 375 grn arrow - so this will be effected more than a heavier arrow.
I also have them closer to the center - as I feel this helps with noise.
Thats with both of them on - but I also shoot with just one on - and seems to do almost as good - with less fps loss

- just wait for one to fly off
But with both its around 6 fps for me.