String gauges for nut on Gretsch G5260 Baritone

So I'm getting this guitar, but I want to put a D'Addario 8 string set on it with the lowest string going down to .80. I think that's probably what I need to hold a consistent drop F/E tuning. With the current .72 being good but floppy when going to Gb or lower.

Though I'm getting mixed results about what to do with the nut. Do I need to file the nut to make space for the .80? Or should the standard nut made for .72 be enough space for it to fit?

Thanks in advance for your answers :)