h1b transfer - premium process

i need to file a h1b transfer, by premium process. but does anyone know if they would come back and ask for more documents? (补件)??? i am really worried about the timing. if i tell the new employer that i need 3 weeks to process the transfer. but at the end of the third week, INS faxes back notice asking for more documents, that is going to screw up my offer!! Does anyone have any suggestions>>>???? Please help!!!!!!!!!!!!!!