Longer string could help. It’s a pretty tight formation, so any extra space you can get helps. If you have a smaller yoyo, that might also help it fit through the openings.
If you are not already, you also want to make sure you have the ladder formed as much as possible before landing the yoyo back on the string. It is harder to open up the formation once the yoyo is mounted, because it will be sitting on the string pulling things tight. Making sure the openings are already as large as you can get them before that can help.
You can try to open up the formation up a bit more after mounting the yoyo by sliding the strings around manually. You don’t need them all to be big, just the one you are passing the yoyo through, so repositioning the strings to make that one big at the cost of the others can help. Once you get more used to it, you can try working toward doing the trick without having to reposition any strings, but that can help for learning. It is a pretty tight fit that takes a lot of accuracy with the yoyo, so keep practicing and it should become more doable as you get used to the maneuver.