Flashed NEC 2500 - Dual Layer Problem



Hi-I have an NEC 2500 that I flashed and now shows as an ND2510A.

I’ve just tried to make a dual layer disc for the first time-Nero Burning Rom allow me to create the file (A mixture of compressed audio just below it’s maximum), the DL disc identifies ok in Nero, but when I come to burn, I get a message from Nero saying it cannot burn as there is insufficient space. I know I’m not oversized, so anyone any idea what the problem might be?