How to make a netbootinstall from an instadmg image?

Hi. First; I have to take my hat off for the application! Now i have made an image, i use netboot a lot and would love to convert my image to a netboot install .nbi. I can't find any info about it anywere does someone have any great tips or howto? Im using Leopardserver, tried to mout the image, and the use System Image Utility without success, got an error at the cleaning up fase.. thx p