I'm assuming this device will have the screen slide out instead of just the keyboard like the mod. So I was wondering if you thought about slapping a second (thin) battery behind the screen or would that cost too much?

Wouldn't that upset the balance of the device?

I don't think so, the keyboard, battery, SoC etc. is on the bottom half, it's just the screen (maybe speaker(s) too) adding a thin battery behind the display shouldn't affect it.

I don't think, that a second battery under the screen makes much sense. In my opinion one device one battery. But I think the battery should be changeable.

There is only one reason i could imagine a second battery makes sense: When the second battery is just for caching to make the main battery hot swapable.

I agree with Fellfrosch, but this is just my uneducated point of view. I have no skills in engineering and designing electronic devices.

A second battery will be only useful for hot swap, it was used in some rugged phones with logistics etc.

For general users I don't think it's necessary as long as the battery is removable. As adding a secondary battery will lead complexity and add unnecessary thickness.

well what I wouldn't classify as unecessary thickness would be to have dual front facing stereo speakers, not sure where one would place them (outer edge of keyboard side, or on the display side), I would like them either way

Like the idea of chenPhone showing up one day ready to ship. No heads up, no notifications.

Regarding screens. Depends of the purpose of this project. But obviously a more advance screen solution is preferred, unless it makes the device too expensive.

I'll drop my bit here. As it was said before I don't think that bezelless screen is any better. It will probably add to the price as well as being slightly more fragile (just a guess). But what I would love to see is a device available for anyone. There is so many people out there wanting to have device like this. I'm still using n900 as my second device. And just by accident (playing a computer game) I came across a guy who uses SF mobile. And there is so many more out there. I was so looking forward to neo900, but now it looks like it will never happen. What I'm trying to say is that there is a huge market out there plus on top of that there is a ton of people tired of using android and iOS just eager to try something else. I reckon with right campaign this project has a potential to became a hit. It's definitely a move in the right direction.

Another interesting thing was that Qualcomm introduced a new tier of SoC's, the 700 series, being better than mid-range but lower than the flagship level.

Could mean we could go with a SoC from this series, or it could mean the mid-range 600 series could drop in price and use that instead.