Re: How can I clone my N900?
 

Just flash the stock kernel to the new device, then restore your backup images. With PK, at least, the stock kernel's modules still exist on the rootfs, so it'll boot with either the PK kernel version installed or stock.
I've found that flashing to stock, restoring your images, booting, and then reinstalling PK works a treat for moving to a new device.

Re: How can I clone my N900?
 

Will that work even if one uninstalled stock kernel after installing KP?