The retail option in the recovery disk only sets the dashboard.xbx to retail 360 dash instead of xshell. but it still a dev kit.
also dev kits can shadowboot into rgloader which is patch more like a modded retail.
the external wont work inside the 360 as it formated as fat32 and the 360 use a special format (which will wipe the drive if you choose to do it).
you can do it but like i said it will wipe the drive to XFAT format.
modded xbox remove the ss.bin check for the hdd. when you wipe the drive it wipe the security file with it.
i know some hdd can flash with the ss.bin to turn into 360 hdd.
Xell is still required to boot but you get the xell text info by a 3.3v usb-ttl device hooking to the rx port on the 360 motherboard.
I did this to a xenon years ago for xell, at the time only component cable can view the screen and i did not have a tv with component.
some pics be nice. the only xdk one x I saw was a demo one before it was released.
It was sad that I knew more about the kit than the MS employee they had show casing it lol
hell had a modded 360 before modded dash/kernel rebooters were out. Way before 90% of the people give a damn about them as well. I still got my first modded 360 from the smc(jtag) exploit, a ****** glitching jasper and a xdk slim. which i use the xdk a lot since it dont freeze a lot like my rgh...
But the op said xebuild, you can go to thoes dash if the xbox allows it. ie fats can only load 7*** kernel and to go way lower a xenon/zephyr would be needed.
and no one made patches for the older kernels so that would be needed if you want it modded.
there is a file called dashboard.xbx on the nand where it set to dash.xex instead of xshell.xex.
best way is to run a recovery or dig to figure out on how to replace that file.
can it be possible to shadowboot into a retail, just like how rgloader patch the bootloader/kernel to run on a retail cpu. but backwards boot into a retail from a xdk?