The program is fine! I burn all my DL discs with ImgBurn. But I make the ISO with PgcEdit. I always select "Seamless" and never had any problems, you won't notice the layerbreak at all. Normally I select a layerbreak position so both layers are about the same size but it really doesn't matter very much. I don't select "don't update ifo/bup files" (I think otherwise the layerbreak/seamless you just selected is ignored and the layerbreak from the ISO is used but I'm not sure).