My guess is that they'll use the same code in GT6 to handle multi-monitor, so your 90 degree trick should still be there, if not at launch time.
Forza used essentially the same multi-monitor support in all Forzas (1, 2, 3 and 4). In Forza 4, they removed a useful function, which was the ability to put the HUD instruments on a side screen, thus providing an uncluttered road view on the center monitor.
Now I have to display my ignorance with a question which is important to me.
In GT5, how is DLC handled across multiple PS3s in multi-screen mode, and how is it handled if some online players don't have the same DLC packs as I do?
Reason I'm asking is that things got very convoluted in Forza 4 regarding DLC, and I'm hoping that it's simpler in GT5 (and hopefully GT6). Here's how Forza works. For most DLC in Forza, they'd give away one car in a car pack which would allow all of the cars in the DLC pack to be rendered, but only the free one to be driven. This meant that if I was racing against a friend online in a paid-for DLC car, he could see my car even if he had not paid for it, so long as he installed the free car out of the set. He could drive only the free one of course.
So far so good. That's a workable solution.
Then along came the Porsche pack, all $30 of it. In this pack, there was no free car. The consequence of this was that unless my friend bought the $30 Porsche pack, he could not see any Porsche I drove. What he'd see is something similar to a VW Jetta with black paint.
It gets worse. His console would calculate collisions based on the size of the Jetta, and so if I drove my little 550 Spyder too close to him, he'd perceive a collision when there wasn't one.
And there's more bad news about the Forza implementation. Unless I bought and paid for the $30 Porsche pack under three different GamerTags, my cockpit view would show 550 Spyder on the center screen and Jetta interior on the side screens. This is definitely uncool. There is a workaround which involves sequentially logging into each of the client Xboxes with my GamerTag, starting up Forza, logging out, moving to the next Xbox and so on. If any Xbox froze during online play, I was out of the online game until I had rebooted all the Xboxes sequentially as above.
So, pardon my paranoia, and my PS3/GT5 ignorance, but should I expect any strange DLC behavior in multi-screen GT5?