Need some advice on mixing 2 audio tracks together...

I've got a line on an older film that I've been looking for for a while: "High Road To China" (http://www.imdb.com/title/tt0085678/) starring Tom Selleck.

Unfortunately the primary audio track is Russian (?) 5.0.  The English track is only 2.0.

As far as I can tell the non-English track is only an overdub in the center channel leaving the L/R/SR/SL clean and untouched (including English dialog that can be heard ambiently).

Am I crazy to think that I can take the 2.0 track, mix the channels together 50/50 and use it as a replacement center channel to create a new 5.0 mix in English?

For the life of me I can't figure why it wouldn't work.  Using something like Sony's SoundForge to mix the L/R of the 2.0 mix, decode and extract the 4 useful channels to wave and then re-encode the whole thing back to DD.

Thoughts?  Interest?  Advice?

You probably shouldn't just do L+R of the stereo and slap that in as the center channel, you want as little as possible of the L and R in the center...
You could do passive or active matrix decoding/upmixing (dpl or dpl+) of the 2.0 and use the resulting center channel, that might be ok.
Assuming that the 5.0 is a real 5.0 mix and not just an upmix itself, otherwise there's no point of course.

Hmm.  That IS a good point.  It does seem stronger, but I'll have to compare a DPL decoding of the 2.0 versus the 5.0.   Mind you that's also assuming it's 2.0 stereo and not 2 channel mono (something else I forgot to check).

Anyway, that's a good idea about extracting the center from a DPL matrix.  (If I can figure out how to do that again.)

Applying Dolby Prologic IIx made all speakers except the center go dead on the English 2.0 track.  Looks like 2-channel mono.

Would doing something like using English mono minus the L & R channels of the Russian 5.0 track make a good center channel (assuming they sync properly) or would that still not be quite right?

Edit: OK.  Never mind.  Testing the Russian track further: L minus R and R minus L completely neutralizes the channels.  Definitely not any sort of true surround.  I assume the surrounds have some sort of delay applied.

Not worth the effort.