Stupidly, I just burnt a >4.7G image onto a DL disc.
Imgburn simply threw up a warning in the log about no layer break info to be found in the MDS file, then proceeded to perfectly burn the disc just as I asked it to (creating the layer break 50% into the image).
Can a warning dialog be presented in this situation so next time I accedently put a DL instead of a SL I can bail.
Thanks for a fantastic program!
N.