Is there a way to specify a callsign, something other than Air Force (which didn't work when I tried it), NAVY, etc., so Pilot2ATC will recognize?

It's not set up for such call signs.

You can use a GA call sign with the CallSign code as Mfg and at least 3 digits/alphas as the tail number.

So, for example, Drummer 33 does not work, but Drummer 133 or Drummer N33 does.

I'll add this to the future enhancements list.

Dave

Thank you, I really appreciate your looking into this for an enhancement.

Jim

It will be available in the next update. 

Dave