I think it will work, that said, the chances of failure imo are higher with your technique, that's all. How your body falls will likely determine whether or not the rope continues to apply pressure on the noose for the 20 mins needed to ensure death. Your not using gravity to choke yourself out, your using force exerted by your actions that will not be available once your passed out. How much rope do you have from the tie off point to the noose? If it's too long for example you'll simply fall on the floor and the noose will not apply any pressure at all, you'll 100% wake up in that scenario.
Many also fail, the unabomber failed, war machine failed, to name a couple, only documented because they were in prison.
I don't want to scare you, it's more of a fear I have myself tbh, that's why I know all this.