Use of an EM simulator appears to be in order to get a meaningful field pattern and input impedance. My cheap FM stereo antenna works great when I bend it in the middle (approximately) to get the best pickup in my somewhat rural location.
A couple free EM programs are available on the "Antenna, Electromagnetics & Transmission Line Simulators" area on the software page.
Let us know what you come up with.
- Kirt Blattenberger