maybe just use the availabe (supported) wheeels in GT5. Helped me as my wheel (fanatec) is also not officialy supported. (i took the Thrustmaster 500 one)
You´re mixing things up a bit, I guess. Just because a wheel isn´t officially supported doesn´t mean, you can't use it properly. The Fanatec wheels work flawlessly with GT5, as do the "unsupported" Logitech wheels.
By the way, what exactly do you understand for "officially supported"?
For me: Official supported = available in game in the controller menu.
I used to pick some DFGT priorly and it did not offer all the settings (keybind and FF support). I then choosed the T500 for my GT3 v2 as they seemed "comparable" in quality and price (with CSP).