So, after reviewing the antenna design and characterizing the FR4 material, it has become apparent to me that my initial log-periodic design is simply incorrect.  The substrate permittivity only affects the feed line line impedance and does not change the phase velocity of the radiators.  As a result the antenna simply does not work, and would need to be twice as large to operate correctly.  A board that large would be prohibitively expensive for a single antenna, so I've decided to pivot to a patch-based array design that is dual polarized.  This effectively gives me two antennas in the same footprint and should also improve better beam symmetry.  My prototype patch layout is shown below.

Once I've verified the resonant frequency of the patch, and the port isolation, I'll complete the array layout.    The final design will contain four patches in a grid layout with combiners and impedance matching to produce the broadside radiation pattern. The final board dimensions are expected to be 8 in. x 8 in.