I just did a few measurements experiments based on the Gamepad's screen. I think that Nintendo will actually want to keep the bezel as thin as possible. The reports that there isn't a camera on the main unit may lend credence to this. Also, one of the main benefits of Samsung's free form display is an extremely thin bezel. Perhaps Nintendo ditched the elliptical-shaped screen, but still heard the criticisms of the Gamepad's ridiculous bezels and empty space.
All this in mind, I'm thinking slightly shorter than your suggestion. 3.5". This is about the height of a bezel-free Gamepad screen and also about the height of the 3DS XL bottom. So it would actually be workable as a portable at least as much as that device.
This is precisely why i clearly said: "4'' give or take". i though about it some time ago but i remember that if designing the controllers centering around an almost bezel less 6.2" screen the lenght of the halfs would amount to something like 3.66".
Since there's no way to asure Nintendo would go with something like Sharp's Free Form Display, 4'' is a safe estimate for a less costly and more conventional LCD.
I think that keeping the controller attachments at that short length would help alleviate that uncomfortable amount of empty space between the circle pads and buttons/dpad that you reference. The other thing is that I think they could leave some empty space at the bottom (right in horizontal mode) and still have it be comfortable. I am testing this hypothesis on the Wii Remote which has space beneath the "2" button comparable to what I'm thinking. Personally, I can use the Wii Remote comfortably this way. In fact, I even find it playable with a Motion Plus attached, but that's a bit extreme.
I agree that it would be worth it. The other thing they could do is one long paddle, but with different switches on the circuit board inside that pick up whether you are pressing on the top or bottom. With a shorter controller, these would be reachable by at least the ring finger and pinky even when held vertically.
The other interesting thing about these 3.5" controllers is that they might even be able to attach long ways. That would give you a single controller about the length of a Wii Remote able to be used horizontally or vertically. They wouldn't even need to connect physically, but there could be a silicon or plastic shell to hold them next to each other.
i made some mock ups even previous to all this NX rumors that have incorporated those ideas.
They work as both a traditional 2 handed control and as Free Degrees of Freedom controller. Although they are centered around simplifying the interface and making it more natural and intutive. On the other hand Nintendo seems to be focusing in keeping their traditional inputs while accomodating games through out generations of Nintendo hardware from NES to Wii U.
Here's one example:
http://m.neogaf.com/showthread.php?t=475774&page=100000
Interesting enough is a 3.66" in size.
I definitely think that two shoulder buttons would come in handy for games that only use the center NX unit. With the width of the controllers around 1.25", they would be nearly the same width as the Wii Remote and sides of the 3DS XL. I'd imagine these shoulder buttons would be just as reachable as ZL and ZR on a new 3DS.They'd be a bit further in than the new3DS ZL/ZR, but still reachable.
Two shoulder buttons coupled with a multi touch screen would enhance the interactivity of mobile games without complicating the user interface, ending up in deeper and better controlling games for this sector.
There's the added benefit of keeping a more or less "robust" input system when the controllers are detached while making the console more portable and easier to carry around.
Not to mention that is not coincidence that the 2 more succesful Nintendo consoles with the mainstream audience, the NES and Wii, have implemented 2 main action buttons as a control method. This seems to be the sweet spot of button complexity that the general public is willing to handle.
And even for a more seasoned player, 2 physical shoulder buttons in "tablet mode" would complement rather well various thumb operated virtual buttons.
Of course, we should also wonder if there are going to be optical sensors on the controllers. Digitimes, if their report is worth anything, has repeatedly insisted that PixArt have been sourced as a supplier for something.
If PixArt involvement is true, it could only mean good things for the capabilities of these controllers. Since the company specializes in image sensors like the Wii Remote IRC, either something like using those for tracking button presses, gesture recognition or a more robust spatial orientation would be in the cards.
Image Sensors was the thing that triggered this interchange in the first place.
