This one gets debated a lot but the answer is really quite simple. The edge may be thin but it’s certainly there.
There’s a lot of ways to explain it that gets you to the right answer.
If a machine has a 95% payback and you get a free shot after every 10 hands (a single 2x out of 10) you could
take 95 and multiply it by 11 (1045), then divide it by 10 (104.5) and that’s your return – 104.5%.
Whatever game you’re playing on UltX is gonna be a play unless the base game payback is 91% (BE) or less.