I didn't notice a dead spot on my SP5 last night. I have Elixir strings on it. Might be worth tuning down the string in question, making sure it's not twisted along it's length, and then retune.
I was perusing FretNation and was floored by how many sets they carry to fit long-scale Dingwalls now. I see D'addario NYXL, GHS Pressurewound, and Stringjoy sets that they didn't have last time I owned a long scale, plus SIT Powerwound, Dunlop Super Bright nickel, and the Spector fanned fret sets. What a time to be alive.
I'm perfectly pleased with the Dingwall brand nickels, but now I want to go down the rabbit hole.
EDIT: ordered the Super Bright set. I loved them on my Super P, so let's hear them on the AB!