I have tried that too, but for some reason the video from Sorenson gives me some white blanking throughout the whole video. I guess its a codec thing, but everything is transcoded to dnx and exported same as source.
It is just a single clip (dnxHD185) so it should be fine.
I did test the same clip in adobe media encoder and that works perfect. It has always been some issues with the mpeg4 encoding in Squeeze so I guess this is just another of them. Thanks anyway, mixdown probably works fine.
Btw, be careful with squeeze with versions before 8 when exporting H.264. The Mainconcept encoder takes 709 levels, not RGB. If you give it RGB, your .mp4 will look too contrasty (because levels are expanded twice). This has changed in v8 and now it takes RGB for about everything.
I still don't understand why after all these years Sorenson doesn't interpret levels correctly and/or won't let you choose to set it manualy.