For full TCP packet costomization i would suggest hping it's my favorite for *nix i tried to port it to windows though it was beyond my skill level. So if you have a *nix box get Either FragRouter,Spak,or hping. But if not download a *nix emulator with the gcc package so you can use it's filestructure to install and run those *nix programs. I suggest a few programs such as UWIN from bell labs, Cygwin (try to stay away from it) from Redhat, and MKS toolkit also known as NutCracker from MKS Software. If anyone would like to take a shot at porting hping that would be wonderful also it's not a verybig program you just get alot of parse errors in if.h and socket.h.
.:v3n0m:.