I did the in-the-earcup thing for a while, however found that whatever I said would be picked up much louder due to my jaw making so damn much noise (similar to those fancy bone microphones firefighters use). Now I use an extra Davie Clark with a Lav (lapel) mic put inside, the cups taped together. Mic goes to a cheap-o voice recorder's mic plug. Picks up just enough ambient engine noise so you can hear power changes, ETL vibrato, etc and everyone's speech volume is equal. We have plenty of ICS plugs on our helicopter, though a splitter could be fashioned by a smart electrician if you're running low on plug ins.
I've also used the in-the-extra-headset bit with a wireless transmitter for video outside the helicopter, such as video for classes on hoisting. Makes it a lot easier than recording it on a voice recorder, then using some form of post processing to mix it.
-Mike