White border on prints

When doing white matted prints do you also do a white border on the print? If yes what size border looks best.

I used to use a 1/2" border and sign the print in the margin. I'm trying something different now. I'm doing a project for my pastor. I'm printing a 20 x 30 photo on 24 x 36 photo paper. I'll sign the print below the actual picture and cut the mat to show the signature (~1/2" margin around the print).

Hope this helps.