Garbage
I have never seen a double deck super fun 21. The payout is 6-5?
No, it's even worse. Blackjacks at Superfun pay even money. Blackjacks with both cards being diamonds pay 2 to 1 (1 out of 16 blackjacks). Blackjacks win automatically vs. dealer blackjack, but you can also make the insurance bet if you want; it pays 2 to 1.
The double deck Superfun at the three stores I mentioned all have terrible penetration. The casinos would rather make less total profit than make more total profit, but risk losing to the occasional skilled player. The double deck Superfun at the venues I mentioned is unplayable. As a matter of fact, the regular (single deck) Superfun is unplayable at Fiesta Henderson, Sunset Station, and Silverton, too. Paranoia has overruled common sense at all three casinos.