I see that the kernel I cannot get working yet is 4.2.0-0.rc2 (I have rc6 on f23a and still would need to patch that for wifi), but I can't figure out which uboot is on the image.
The messages on the serial console tell the U-Boot version. "U-Boot SPL 2015.07-rc1-00513-g5bcec54 (Jun 11 2015 - 09:17:41)"
Plus whatever is there was part of the pre-alpha, as my understanding, you would have to dd any new .bin to the boot SD card.
Correct. boards.d/cubietruck.sh has the options you need to pass to dd for cubietruck.
Oh, also all you really need on the SD card is uboot. You can put all the rest on your sata drive. A USB drive does not work yet, but Hans says it would not be hard for someone that knows dracut to work that out and provide the instructions to get included upstream.
dracut has a --add-drivers option which you could try out. eg. while I was testing out some drivers, the dracut command I used with a F22 kernel with CentOS rootfs was dracut --verbose --add-drivers "mmci" ~/initramfs-test.img 4.0.0-0.rc5.git4.1.fc22.armv7hl
Regards Mandar Joshi