Right, no need to loop both legs - I didn't phrase that well. To avoid holding up the ride, just unloop your leg while your ride vehicle is waiting its turn to go to the loading platform - it doesn't take any more time than removing items from the seat pouches does. Luckily there aren't any continuously loading fast rides. I personally wouldn't trust my calf power to hold a bag in place on a ride such as Indy with open-sided vehicles, but wearing the backpack backwards is another option.
Your calves aren't holding the bag in place. Coasters are designed to keep people in them, including a large item on the floor in the vehicle. On a ride like screaming, you're really just using your legs to make sure there's no space for a backpack to squeeze out. On some rides, like Screaming, Space and RSR there really isn't a lot of room to unloop the backpack in the vehicle, especially if you have big feet. And those are all rides that will time out. On Matterhorn, looping or wearing the bag backwards works great. I'd put Indy and BTMRR in the middle. And Indy is the ride where I had something fly out of a bag that was buckled shut. Now I put small items in the zippered part. On Star Tours a decent sized backpack that isn't overstuffed will fit under the seat. On Soarin people just leave their bags on the ground and they're sitting there when the ride comes back down. This is one of those things. Disney allows bags on rides now. But it's worth taking a few seconds to secure the bag and your items in a way that helps make sure they keep allowing the bags on rides. If things regularly are flying off rides or rides are timing out because people aren't collecting their things fast enough they might rethink allowing them.
