Same issue, I believe it's a bug only when you use scheduled charging. I was able to change the charging limit successfully when not having the scheduled charging selected. Then when going back to scheduled charging whatever limit you have it set to can't be changed. It will let you change it...
The Ruffland large does fit, it should also fit 2 side by side. I have risers on the removable floor piece to make the rear floor flush. Tied down on to the floor anchors and rear second row seats. We have a 70lb Rotty.