Hi All!
I have been watching this topic with interest. I have worked with patches on DoD projects since 1986. There are many good books about them. Basically, in many ways, in the far field, the directivity looks the same as a dipole. But they are NOT dipoles. They are in fact, a resonant cavity structures formed by the top and bottom plates, with the dielectric in between. The losses primarily are for the volume of dielectric. Metals can only get so good, but of course, corrosion is bad. Difference in copper vs. silver will not be measurable. Make sure the metal is thick enough to support at least 3 skin depths of the signal. At 1.4 Ghz, less of a problem than 400 MHz where the wavelength is .75 m.
Dielectric > 1 has the benefit of shrinking the patch size due to the foreshortening of wavelength due to the dielectric. However any dielectric constant greater than air (vacuo) in Er is going to have a loss tangent associated with it and so the EFFICIENCY of the feed goes down. In RA this can be important. That's why air dielectric feeds are so good, but so big. Rogers material for dielectric filled patches with Er > 1, is very good. Crane Polyflon pure Teflon copper clad material is GREAT but Er is only 2.2 or so so th reduction in size is not much.
Additionally the feed illumination angle is better (smaller) in air dielectric feeds.
The feed beamwidth should be matched to the disk illumination angle. Dipole-like feed work best in f/D ratio dishes less than .25 (Angle about 180 degrees).
Most "figure of revolution" parabolas for sat work are .36 or so (feed angle about 120 degrees or so for 12 dB edge taper).
Offset fed dishes (parabolic segments) have f/D ratios greater than this (about .5-.7) so need horns with tighter beamwidth and smaller illumination angles.
Patches with wider beamwidth (thats why they are great for GPS, full sky coverage) may OVER illuminate a dish, causing spillover and allowing :thermal pollution" from the ground, etc to raise your system noise temperature to levels that mask weak sources.
However, I am also a ham and a life member of SARA. So try your feeds out. If they work for you, great! I just wanted to present some additional data. Anyway, I could go on but I have bored you enough.
J.Kruth