I did my front and rear bench. I found it easier to turn it inside out and put the covers in the dryer for a few seconds, it softens the vinyl making it easier to work. OR if it's a very warm/sunny day, you can do it outside.
Again i must say comparing bench covers to buckets is like apples to oranges. Big difference !
Your post reminds me of my teens. Took mom sofa cushions apart and ran them through wash and dry. They shrank/shrunk ! Never fit or looked right again.
Learned the zippers on the covers were not meant for this purpose.:axe: