The connection is a tight one. Where you sit doesn't really matter since you are arriving at a busy time for Customs anyway. But the true rate limiting step is how quickly your checked luggage comes down the chute, and how quickly you can re-clear security to be allowed in the terminal to catch your domestic connection.

You have three choices:

1.) Leave things as they are... if you miss the connection, you will be protected on the next flight to RDU, usually about one hour later.

2.) Call DL and ask to be rebooked onto the following RDU flight from the one you are currently on... the you will have a very comfy 2:30 (more or less) connection.

And the third option, a bit more controversial, is to leave things the way they are, and if the luggage is delayed coming down the chute, just walk away from it, clear security and catch your flight. When you get to RDU, go to the DL baggage office and file a claim. (Someone from DL will take your bags through Customs and they will often be on the next RDU flight!) I would rate this the least desirable option.