A word of warning about modifying anything in the Paypal user agreement.
I recently read an online account of an E-Bay vendor who sold a $900 item to a person who asked that he send the item to an alternate address than listed by Paypal (the customer supposedly wanted to send the item as a gift). The item was delivered, then the buyer disputed the charge, and the money was returned to her, based on the fact the package was not delivered to her, and that the alternate addressee would not verify that the package was delivered to her either. What a scam.
The moral of this story is that if you allow the script to be changed in a Paypal transaction, Paypal will not support you. I don't know if this applies to splitting the Paypal transaction, as happened here, but I suspect it would.
Babolat PDGT w/Solinco Revolution 18 @ 30lbs