When you say "send".... you just want to get the MIDI composition from Caustic into the DAW?
I mean, just go to Export, and select MIDI as the format. I'd just export all the individual tracks one by one so they can be named and stored unambiguously, then you can just drag and drop them into the Reaper workspace, arm an instrument on the channel, and you're away.
Have you try to check "One midi channel per instrument (1..14) in the MIDI tab ?
http://pquenin.free.fr/pqnaudio
http://www.soundclick.com/thepqueninproject
When you say "send".... you just want to get the MIDI composition from Caustic into the DAW?
I mean, just go to Export, and select MIDI as the format. I'd just export all the individual tracks one by one so they can be named and stored unambiguously, then you can just drag and drop them into the Reaper workspace, arm an instrument on the channel, and you're away.
Edit; just noticed this was >6mths ago, doh!