I dunno if this is the recipe you were looking at, but I did do this a couple years ago and enjoyed it tremendously:
I suggest using SP in the mash/partial mash, and my strategy has been to include some 6-row to try to convert the starches to sugar.
I also suggest caramelizing it first, rather than adding raw potato - but I've never tried it raw, so maybe it'll work...
Finally, I and the few other brave SP-users have tended to find that you can't taste any kind of sweet-potato-ness in the final beer. I don't yet know if that is a good or bad thing.