I tried to achieve Matt's setup in my VM with Ubuntu and Debian (both having their separate /boot partition). Everything worked smoothly, but enabling TrueCrypt-FDE on Windows, I could still access the two grub's, but booting either Linux from there failed.
TrueCrypt actually warned me about multiple OS's on the same disk, but I wanted pre-boot-auth (which only seemed possible with FDE and not partition encryption) and Matt's (btw great!) tutorial implied it is possible.
So where did I fail? Is pre-boot-auth on a multi-boot system stiil possible?