First, Disclaimer: I really don’t know what I’m doing for lag testing. I do not own a TV at all let alone a CRT, so the method below is all I could really think of.
NTSC Megadrive and SNES should be ok, it needs to be something like a Saturn that has a refresh in the region of 59.82Hz (as shown on the OSSCs LCD).
The DVDOs calculate how much lag they’re adding and it’s been verified as accurate in most cases. Make sure your Duo is in game mode, then connect your Saturn (if you have one) and power everything up so the Saturn is displayed through your Duo. Now, go into the menu on the Duo and choose settings->audio settings->adjust audio delay. Drag the slider control as far down as possible into minus numbers.. when it gets to the bottom this is the delay the Duo is adding (or thinks it is). Now do the same with the SNES. If it’s the same as the DVDO Edge there should be more lag with the Saturn. If there isn’t, please let me know right away 🙂