I use the following:
1) Align via preferred method (stretch in Vegas/Reaper or time-align in Audacity)
2) Determine what I like about either source (sbd has less reverberation in the 1-3khz range, aud has a warm gooey bass, etc), and EQ to bring out what I like about both, maybe a net change of 2db tops, just enough to nudge it in a direction. Don't overdo it.
3) Make sure the peaks in either are at least -6 or lower.
3.5) double check alignment.
4) Render to 2ch. (Assuming a render is required to apply editing to both sources equally)
5) EQ/process anything else.
6) Amplify the remaining db and do any limiting and dither.
I used to keep the peaks between -3 and -6 which mathematically should bring your render to just under 0, but I kept having the occasional overage and having to redo the render so I figured the additional few DB of amping in Ozone or whatever is clean enough I'm not worried about it. Make sure to double check your alignment, I prefer to check mine now over the course of a couple of listening sessions and in both loud and quiet sections throughout the recording since non-clocked sources can drift at different speeds (ever so slightly which is a pisser but usually not much of a problem). I don't think I've forgotten anything....