Speaker placement: 6.1 rear or 7.1 front high?

IMO the entire notion of front highs is bizarre. Not that I could use them anyway, as my L/R are almost four feet high and extend to the ceiling. At any rate, the reason for surround sound is to do just that, surround you in sound. You don't get surrounded by placing surrounds in front of you.

I would place the height speakers as high and wide as possible. Will help turn the circle of sound you currently have into more of bubble of sound (adding a vertical dimension).

With 7.1 the usual placement is L/C/R with two sides and two rears. As for content, it used to be that surrounds were mostly ambient sounds, intended to impart a feeling of 'space', but now more and more the surrounds are being fed discreet directional content. I think it would be odd to hear something that's supposed to be panned hard left coming from front left. I don't know what the intent is of 'front surrounds', the term being an oxymoron anyway.

Mixes vary, with some titles making occasional use of the surround-back channels (Super-8) while other soundtracks have surround-back channels that are just as active as the surround channels (Transformers 3). Still, there are over 600 Blu-rays with discrete 7.1 soundtracks, so plenty to choose from.

Besides, you can use PLIIx on 5.1 soundtracks to steer the 2 surround channels across 4 surround speakers. My first 7.1-speaker set-up was in 1991; discrete 5.1 content was still 3 years away (7.1-channel material was 15 years away). So a 7.1-speaker set-up can be useful even for sources that aren't 7.1 discrete channels.

Happens all the time at movie theatres. If you're sitting in the midlle of the theatre, you'll notice that the surround speaker arrays start well forward of your listening position. Doesn't seem to elicit complaints. It's only an oxymoron IF you believe surrounds should be limited to the rear hemisphere. Understand that there are those that consider being surrounded as including sounds in the front hemisphere as well. The industry seems to have settled on labeling front surround speakers as "heights" and "wides", which should avoid the semantic argument you're making.

Research into surround sound has shown that the locations for additional speakers that yield the greatest sense of spaciousness are around ±55-60° from centre. That's where Audyssey and DTS place their wide speakers. Floyd Toole says he likes to place his surround speakers well forward of the listening position (as part of a 7-speaker layout). I tend to prefer my side speakers slightly forward of me, to help stretch out the front soundstage (I run 7 speakers as well).

They're not behind the screen. Sorry, but I'm just a simple acoustical engineer who doesn't see the value in having speakers that supposedly carry surround information placed on the same plane as the L/C/R, where whatever content they carry would be handled just fine by the L/C/R. That assumes, of course, that the content of the front surround signal is actually mixed to be heard coming from the front of the room.

I thought the front height L/R were just that: front height speakers, not surrounds. Not so oxymoronic, then, right?

Seriously, though, aren't the front heights in a 7.1 set-up supposed to be tasked with sounds coming from elevation? That's what this note from dts.com led me to believe:

Nor are wides and heights. There was a time when people felt that a mono surround channel and 2 surround speakers were enough to provide wrap-around envelopment. But that eventually changed, as folks found out that 4 speakers do a better of surrounding the listener than 2 speakers could.

Likewise, there are many that currently believe that 3 speakers are enough in front of the listener. But that's starting to change, as folks find out that wide speakers help blend the gap between the front soundstage and surround field, as well as provide a greater sense of spaciousness when speakers are placed at those locations.

The argument for heights is even simpler: the easiest and most reliable way to get stable imaging above you is by placing speakers above you. Nothing unreasonable about that. Current approach is to use a pair of speakers placed higher and wider than the mains; DTS might be adding a second pair of heights placed higher and wider than the surround-back speakers.

If you're getting everything you want from your L/C/Rs, then there is no compelling reason for you to add more speakers forward of your listening position. For others, who have heard audible benefits when using heights and wides, it is a useful option to have on newer receivers (like the Onkyo that the OP has).