Perhaps my mishap can help answer your question (but please do your research) - I acquired a Classic Accessories Part Number 73463 for my 2017 26DBH and personally determined that it was "just too snug" to get on mine. IF (please research) your 2021 26DBH is the same measurements as my 2017 26DBH is, then I wish I had gotten the next larger size - it was that close, but not quite... reference:
https://www.amazon.com/Classic-Acces.../dp/B0009I1WYQ - when I used a tape measure from the back of my trailer wall to the front-most bulge, it was 28 feet. Again, this is not a recommendation as much as it is a story about what didn't work