I can't answer. But there are fine web pages about how to shrink a DVD. Even CNet writes about it at http://reviews.cnet.com/4520-6603_7-5141963-1.html
I used that trick last year when our training video exceeded the 4GB mark. But I didn't use a DLDVD at all. I used Alcohol 120% to have an umulated DVD recorder and the software CNet noted to shrink it.
I'm not sure this is the right forum for my question so here it is.
A friend of my just installed a DL DVD burner in a computer with also a regular DVD burner. He "claims" last night by mistake he put a blank DL DVD in his regular burner by mistake and burned a movie on it in the DL mode. I don't feel like trying this at $1.50 a pop just to see if he's right.
So, is it possible to do this in a DL format or did he really "convert" a DL DVD into a single layer?