My understanding of the reason that Safestrap 3.72 isn't released for our phone is that it doesn't support bootstrapping the slots.
If that's true, then you can't do what you want.
Also, if you upgrade, you'll get the Kit Kat kernel, which means that even if you get a slot to boot, you'll need to use bypasslkm to load the modules into that slot (otherwise, no wifi, etc.) But since you're not rooted, you can't run bypasslkm.
My Android devices:
vzw Samsung Galaxy S4 stock NC5 rooted
Samsung Galaxy Tab 2 10.1, also stock but rooted.
VZ Droid Incredible 2 rooted but otherwise stock.
Samsung Galaxy Tab 10.1