Originally Posted by Fat R Inanimate
Jolteon seems like a pretty interesting choice for Double Hall. I think I thought about using it at some point after using Kingdras for Double Hall, but probably ended up writting it off due to not really coming up with a good way to deal with:
H439 | Regice | Quiet | Sitrus Berry | Blizzard | Avalanche | Hyper Beam | Thunder Wave | Atk/SpA
Since it just tanks Discharges like a champ, and survives 2 Specs Thunderbolts, barring criticals, due to Sitrus. Regice also has a decent chance at 2HKOing Jolteon with Blizzards
I'll admit I hadn't thought about Regice in full yet because I had first tried to ensure that Jolteon would have no issues with Ground-type pokes, but I also mentally set it aside because I have a feeling it would try to TW Jolteon instead of using Blizzard straight up. When I was using PZ it always went for this (Specs Hyper Beam wasn't a OHKO or something like that), and you know how some pokes are seemingly programmed to always make the same move on turn 1. Gardevoir always Tricks its Sticky Barb, Aerodactyl always uses Sandstorm, and I would hope that the Regis would do the same and always Thunderwave, and also not "know" that Jolteon has Volt Absorb. We've seem the AL uses water attacks repeatedly on Water Absorb/Storm Drain pokes through many iterations of the tower/frontier/subway, so it's not entirely just wishful thinking!
My main issue with Regice would be its Clear Body, actually, since Fake Tears on Jolteon on at least one sideboard is a fantastic move. Regardless, here are some important calcs (that you've already done but this is mainly for everyone else etc):
Quiet Regice 2v2
vs. 252 Modest Choice Specs Jolteon 2v2 Thunder : 165 - 195 58.1% - 68.7%
vs. 252 Modest Choice Specs Jolteon 2v2 Discharge : 82 - 97 28.9% - 34.2%
vs. 252 Modest Choice Specs Jolteon 2v2 Thunderbolt : 130 - 154 45.8% - 54.2%
vs. 252 Modest Focus Sash Jolteon 2v2 Discharge : 55 - 66 19.4% - 23.2%
So we get the idea of what Jolteon can do to Regice offensively...Regice itself does 45-54% to Jolt with 2v2 Blizzard. Jolteon *does* get Light Screen and is somewhat liberated from having to use Focus Sash when playing Ice Types since Sash is kind of useless against double spread moves, but it would still be kind of tough. If I gave a shit I would probably still strongly theorymon Jolteon since it can still deal with Ground types with Magnet Rise and HP Ice/Ground well enough...
I've been having some pretty bad luck with playing Double Castle so far. Well, more like I can't go 100 battles without overlooking something in preparation. But it's pretty silly how the moment I screw up preparation is also the moment the CPU decide to put Murphy's Law into overdrive. I usually end up needing a turn to get back into control of the battle when I screw up, except that their Quick Claws, Flinching, and Critical Hits have gone 4 for 4 in killing me during that one turn opening.
What are you trying in the Castle right now? Kind of refreshing to see someone else giving the latest Frontier some additional love...