With regard to Thomson posts. They are popular not only because they seem to provide a high degree of strength at a reasonable weight and cost, but, also because they offer a broad rail clamp, both top and bottom that helps support the rails of clyde's saddles and help limit rail bending. There are other posts that offer a similiarly wide clamping surface, they just haven't gained the wide spread support that Thomsons have.
__________________
Birth Certificate, Passport, Marriage License Driver's License and Residency Permit all say I'm a Fred. I guess there's no denying it.