When I read "common sense" and "FAA" together, I had to read the thread!
I had a similar experience. My DAR gave me the standard 25-mile radius for Phase I testing but, having read here on VAF that others had been successful in pleading for a larger area, my DAR went back to his FSDO and requested a 25 x 100-mile corridor, wherever I wanted it.
That worked out really well for giving me plenty of room to do testing, and I located the corridor over a bunch of other airports, which gave me lots of emergency landing fields, just in case.
Sometimes, all you have to do is ask.