Well, I mean there are some real Oppo experts in this thread but I also have one 103 - same as you - and will try to answer the question.
I have to admit, I have never tried it and use HDMI out 1 on the Oppo to my AVP and then HDMI out from the AVP to my projector. In the Oppo thread there were big discussions going on, which HDMI out is better. Usually, you use HDMI 1 for video, because it has the Marvell-Chip connected to it and you can tweak the parameters in the Oppo.
Before HDMI 2, there is 'only' a Mediatek-Chip, if I am not mistaken. There you cannot do 4k or many other things, you can do with the Marvell-Chip. Therefore, a natural choice would be to use HDMI 1 for video and 2 for sound. You can set this in the Oppo menu.
However, some people in the thread reported, that they are experiencing a loss of lip synchronization using this kind of setup, most likely due to different processing times in the respective devices.
Well, if you want to hear my personal opinion: Splitting up the signals, gives you no advantages. I remember that there was some saying about the A1-UD, that you should use different HDMI outs for video and audio. Personally I don't know what the advantage would be? I can think only of disadvantages - two different clocks, two cables etc.
The HDMI cable is capable of transmitting audio and video in 2D without problems, so why splitting it up? But on the other hand, you can just try it out. See for yourself, if this gives you any kind of advantage. Each chain is different and the equipment used also differs. What is in one chain an advantage, can be in another one a disadvantage. Also for 3D, things may be different. I don't have a 3D display.