Hey Bond, I am also in similar situation. I remember having talked about leaving the country in OPT with my International counselor when she gave me a document and told me that with a clear cut offer later, one can leave country and come back with I-20 under F-1 category for the remaining OPT period. I also believe that the new visa will cover only the OPT period. Let me know if u get more info on this. Thanks,