gene - you are closer to the truth than you know! I did try the precompiled archives of 4.02 and 4.05. But before I tried 4.0 I thought it would be wise to try the "grep PXELINUX /usr/share/syslinux/pxelinux.0" method (thanks tinypoodle) to get the actual syslinux version. I found that syslinux in TC 4.7.5 is at version 3.61!
Once I knew that little detail it was not too hard to figure out what to do next! I downloaded the 3.61 binaries from syslinux (thanks for your tip), extracted and copied menu.c32 and pxelinux.0 to /netboot (after running tc-terminal-server) and tried a PXE client boot with a modified 'default' menu. Need I say that it worked? Well, just in case there is any doubt, IT WORKS! I have a functional menu! This has been a battle but it feels good, very good, to have it working.
Thanks to each and every one of you for the help you have given.