Reread your post and don't know where I got the DTS:X bit.
There are suggestions for speaker placement on the Dolby and DTS sites, not sure anything particularly addresses bipole speakers. As you mentioned not much about the now defunct Audyssey DSX, altho some thoughts from various discussions if you search "audyssey dsx speaker placement". I've not used bipole speakers for surrounds for many years previous to my 4520, as I prefer monopole, but I'd think rear surrounds likely the best place for them. The manual starting on page 184 does have some info on what speaker positions and features are relevant to each sound mode.
I've used a 9ch setup with front wides and rear surrounds with my 4520, never got around to wiring/mounting front heights; now I'm back to a 7ch setup with rear surrounds, felt my room a bit narrow for wides. Good luck on finding your optimum setup.
Curious, how big a room do you have?