I have a seat cover that will work great but there are no custom fit options for bench seats on your Pleasure-Way Plateau Motorhome. I recommend the Aries Automotive Seat Defender Bench Seat Protector item # AA3147B. This black cover is 63" wide x 58" tall. It has two covers that go over the headrests with hook-and-loop straps. It also has cutouts that will open so you can access any seat belts.
I have linked a review video below so you can see what this cover looks like and how to set it up. view full answer...
We've checked with SumoSprings in the past with this question and they have told us that between 1/2 inch and 1 inch is standard clearance between the frame and the SumoSprings like the part # SSR-121-47 that you referenced. view full answer...