Best feed for surplus dish?

DirectTV 20" dish, offset fed, f/d~0.7, to be used for 2.4 GHz wlan link.

As I understand the issues, the best feed is one that -- for a given focal length -- will "light" the dish with as spherical a wave as possible, that has a broad enough dispersion angle to fully "paint" the dish without picking up off-the-edge noise.

I've looked at all types of feeds, from cantennas to bi-quads to patch to dual-dipole. All have their pros and cons.

I'd like to hear from anyone who has done this before about what feed they chose and why.

Thanks,