Macbook retina + bootcamp + win7 + external SSD = HELP!

I´m trying to create a bootable bootcamp win7 SSD connected via thunderbolt. And I've followed a step by step guide but I get stuck when I try booting from the SSD.

The procedure is that

1. I've installed win7 using bootcamp to an internal partition
2. Booted up windows, installed bootcamp drivers and thunderbolt lacie drivers (its a lacie rugged SSD usb3/thunderbolt). Got the SSD mounting in windows and everything.
3. Used winclone to clone the win7 partition
4. Used winclone to clone win7 img to SSD
5. Reboot and choose external (showing as internal) SSD
6. Start boot process but stops gets stuck with a blinking cursor in upper left corner.

I've tried deleting the partition but it doesn't help. But if I use winclone and clone the image to new internal partition it works.

Anyone got some tricks I can try or some other way of achieving what I want?

According to some of the guides out there, it isn't impossible, like this one for example:

Set up Bootcamp on an External Thunderbolt Drive

And I've read a couple of forum posts here and there of users using this technique and win7. So I'm not convinced its impossible. Have you tried it yourself?