Great idea! Ah, if only it were that simple, though.

There's actually a whole series of those values there already:
DALNonStandardModesBCD1
DALNonStandardModesBCD2
DALNonStandardModesBCD3
DALNonStandardModesBCD4

And they all simply go up in resolution. In other words,
DALNonStandardModesBCD2 simply picks up where DALNonStandardModesBCD1 leaves off. In fact, it splits in the middle, with DALNonStandardModesBCD1 ending with 1280x720 @ 75hz, and DALNonStandardModesBCD2 picking up at 1280x720 @ 85hz. It's basically several registry entries containing one large sequential increasing list of nonstatndard values.

Although I will try adding my custom rez to the "2" entry and see if it shows up. I'll report back if it does work, otherwise, y'all can assume it didn't work.