I personally don't go for stall tactics in battle maison as you need to play fast for a win streak in a reasonable amount of time (mega evolution animations are bad enough here).
I decided to give super singles a go as I should fare better than I do in super multi (using a Sun team, Aerodactyl or that other rock/flying fossil usually show up sometime and its gg there) and I've got a streak of 46 so far. Had a few close calls. The best was not knowing Cobalion had justified and winding up double sucker punching it with Mega Karn (I knew it outsped me, was fighting and had sacred sword so with that info it seemed like a smart move) leaving only Garchomp to take it on. Garchomp failed to kill it with Earthqukae but survived +2 sacred sword with 2 HP and then rough skin took care of the rest (if it had died Cobalion would have fainted first and I'd have lost...thats how it works, right?).
Oh yeah who was the other team member. Talonflame lead. STAB recoil, roost and tailwind (tailwind suicide may not be the best, especially when you survive turn 1 but 'Karn loves the tailwind), EVs are still an experiment (trying to work out the sweet spot for speed when I need to use flare blitz as gale wings makes it irrelevant for the other moves, I also accidentally gave it 20 defence EVs, which have been surprisingly useful).