I cannot sit in a sling wheelchair. In order to follow Disney’s rule about
ECVs not being in the regular line, I put a rollator on the back of my
scooter. The rollator folds for transporting it and also has a flat hard seat - not a sling seat with very little support.
Perhaps a rollator would be your answer.
We were at Haunted Mansion last year. The CM told us that they had an issue with an
ECV earlier that day when a woman hit several children in line, hurting them so that they needed medical attention. I know that I did not plow into anyone and neither did you - but - I certainly understand why they do not allow ECVs in lines. Disney does not want young children or adults to be hurt at Disney World!
I hope this helps you. Thanks for reading.