You can actually use an arbitrary cross section in the Patran Beam Cross Section tool. As long as you can create an outline, it will allow you to calculate section properties. just set the Action to Arbitrary Shape.
The outside shape of my beam is a simple square, the problem is the inside which is quite complex. I will have a look at the article and see if I manage to do something :)
The articles are there, but the links were wrong. I've corrected them now.
However they may not help: you're right that 8 internal loops is the limit. Perhaps you could join some of your loops to bring the section under the limit? That should at least give an approximate value for K.