Haven't really tried to do this inception thingy for a while but remember I had some problems to playback FL individually when I had it rewired or as VSTi (don't remember which and if I managed to fix that). If you want you can run FL as VSTi plugin or rewire inside reaper and use multi-out possibilities to mix withing reaper. With VST & DX hosting, a flexible 99 insert-track mixer, advanced MIDI, DX and ReWire support no musical style will be beyond your reach. Fruity Loops (FL Studio) is a full-featured music production environment capable of multi-track audio recording, sequencing and mixing for the creation of professional quality music tracks.