Many I do in DVDlab, however, some files lose audio sync during DVDlab's demux and then remux, even though the sync is perfect in the original. I can only guess the reason, but with so many source formats being turned into one format, I'm sure there are a whole myriad of reasons.

But I know the original is perfect when left untouched.

Now, being the smart lad I am, I think I have figured it out.
1) import the Winavi created DVD files. (project 1)
2) import the dummy DVDlab created DVD files. (project 2)
3) In Project 1, right click on "Video Title Set #" and select "Add Language Unit". This creates a subfolder "Menus" under the Title set. This is where I was stumped before. I was expecting to find the words "create menu" or something.
4) Optional: In Project 1, right click on Menus and select "Set Languge Code". This is necessary if you want to make a multi-lanuage DVD.
5) In Project 1, right-click on Menus, and select "Add PGC". This will put a subfolder "PGC1" under the menus.
6) In Project 2, right click on the menu you wish to copy and select "copy PGC"
7) Back to Project 1; right-click Menus and select "add copied PGCs". Do 6 & 7 again if there is more that one menu.
8) In Project 1, right-click PGC1 and Select "Set Menu Catagory/Root Menu"
9) In Project 1, make a command in PGC1 "Link PGC2"
10) In Project 1, Under "Video Manager/First Play" change the command to 'Jump VTS 1 "root" menu (title 1)'

I'm just a newbie to this software, so I am sure there are a few imperfections to this method, but it works for my needs.

Works fine and I'm off now to buy the software.