Hi James
AFAIK, what you are asking (1 IDoc to two systems) cannot be done. 1 IDoc can only be sent through 1 port to 1 system.
If you insist on a single IDoc in the ECC system, then an alternative approach would be to send it to PI, then from PI route it unchanged to WebMethods (in addition to where PI should send it to originally).
Regards
Eng Swee