And you've held it in your hands and tried? Or you're just spouting on the basis of a render?
I made a little test with a box roughly that size, to see what it felt like. I don't believe you'd have to shift grip.
You might want to redo your test. Yes, i did only watch the rendered image, no, i don't for a second think I'm wrong in my opinion. Your playing a game, using the analog sticks, and for any reason you like, you need to hit the B button. (I actually thing the X is even worse, but nevermind that just now.) Just letting go, and pulling your thumb to the right, and you'll end up around the delete button. This is your natural position for the thumb. All the buttons will be pressed by bending up the entire thumb to a none natural position, and pretty much pushing the buttons with the inner joint of the thumb, instead of the natural way, where all the joints work together. Make a simple test. Get your hands on a Playstation 1-2 controller with the analog sticks. Its 14cm wide, or just about. Incidentally, the width of this thing has been estimated to about the same for this handheld. Put your hand on the analog stick. Now move your thumb straight out to the right, until you end up right below the O button (thats B's position.) and hold the thumb there for a minute. Let me know if you think it feel natural. When your done, and like to spend another minute for some rather useless test, retry it with the X button. Oh yeah. What doesn't feel natural is simply since it's not a natural movement. It will give you anything from slight discomfort to aching pain after repetitive motions as from, lets go on a whim here, playing a game for a couple of hours.
Doing a test this way, isn't really accurate, the pad is angled, both out to the sides, and also downwards so it lays better in the hand, but a detail that would ruin the handheld, but is enormously important in a gamepad, is its thickness. The handheld's base is what, 1cm thick or so? (at most) It wont really sit great in your hands, but is one of those sacrifices you have to make to get it portable, instead of "i can put it in my bag, when I'm going away somewhere for a couple of weeks" I for one would hate to have a thing like this cramp the playability of the darn thing, its just not right for something someone spent so much time and effort on.
And yeah, i do return to the PSX gamepad all the time, since lets face it, its the one we want to copy, and its the one everyone else copy. Why? Coz its a darn good pad. I'm mostly going to be playing Snes, and Amiga on mine, if i get one, so i could probably do fine with the current design. Not that I'm getting this if there isn't something done about the clamshell design, so you can turn it outside in, and get a flat square you can use the touchscreen for all your interactions with. I'll simply get the GP2X F-200 instead. I haven't given up hope yet, but one thing is for sure. If it goes in to production in a version i don't feel supports my gaming the way i like it, I'll get the GP2X, and i already know I'll be pleased with the functions that are available on it (It's those that aren't on it I'm missing there.) and when I've bought one, i ain't buying an updated version of the Panda, for another 5-10 years.
And for all those who don't like the name, why do you bother? Everyone say "I'm playing PSX, PS2" not "Playstation." Those getting a "OpenPandora" will simply say "This? Oh, it's a Panda." The games you'll play on it, is most likely emulated games, so you'll say "I'm playing PSX, on the Panda" and so on. I'll tear mine apart, and dye the shell black, and airbrush a "Mr B" on the back of it, if need be, so i don't care much what they call it. Then again, i don't have any friends, so nobody will ever ask what the thing I'm gaming on is called. (Just refreshed the info site, and noticed that they already went with a black look, so i only would have to airbrish the "Mr B" part then...)
B!