We have a 2015 24.1. Originally, we bought a sheet to use on the bed used as a king. It's 92" wide x76" long, so we bought a custom made sheet from Advanced Bedding.
Sheets, Sheet Sets, Custom Sheets for Home, RV, Dorm, Hospital, Hotel, Adjustable Beds | Free Shipping | Advanced Bedding
It was a bit spendy
We have since began using a full size sheet & a twin sheet, so we can access the storage under the bed.
If you do use advanced bedding, they show you how to measure.
congratulations on your new motor home.