Be careful of simulators especially the ones made for PCs.
The math behind that number crunching is fairly complex for
us mere mortals.  Simulator software, at least in my little
research, fall into three main categories:

    1. Mainframe supercrunchers that are really accurate
       and very expensive.
    2. Mini-mainframe packages that sacrifice the accuracy
       of the mainframes and less expensive.
    3. PC style packages that have to sacrifice a lot and
       are inexpensive.

One way that accuracy is compromised is by doing things
like assuming a ground plane, any ground plane that is
in the PCB, is a perfectly conducting ground plane.
I wouldn't know what to recommend in regards to free
software for a PC.

Perhaps, Doug, you may be able to get into a Beta type
agreement with a software mfr of a simulator.  You could
possibly get the software for free and the information
would prove invaluable for both of you.

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