Forget it, and download
PgcEdit_winexe_7.0.1_beta1.zip. Change the Seamless LB state in Options -> Input/Output, and create the ISO normally.
However, I'm pretty sure ImgBurn will clear the seamless flag before burning the image. Maybe you have to use the good old DVD Decrypter? PgcEdit should still support DVDD. Just configure it in the burn setup dialog. Or launch it manually, and configure the LB LBA in its setup dialog.
I haven't a DL DVD to test, so, let me know if ImgBurn or DVDD works.