CW,
No I don't know how flat my table saw is, but I did move the plane
around in a quite a few positions on the table saw top and also on the
extension table top and every place I put it the result was about the
same. So I am pretty sure the plane isn't flat by approximately the
amount stated.

I considered testing it on a flat piece of glass, but how flat is
that? Especially if it is sitting on a non-flat table. Flat is a hard
thing to be absolutely sure about.

DJS