Dog seat cover suggestion?

I bought the cover for the backseat of my 2016 Prius from Treat-A-Dog. Works great, complete coverage, and simple to put on and take off.

 

I have 3 Border Collies with long hair, and my Prius has all black interior. I was really nervous about how the seats would look over time too, I bought 2 different seat covers at Marshall's/TJ Maxx for like $15 each. One is hammock-like for the back seats, and the other just covers the front passenger seat. They work perfectly, and honestly the seats in my Prius are SO EASY to keep clean. Even if I don't use the covers, hair and dirt wipes right off....I still get compliments on how new it looks.

 

I just purchased a 2017 Prius 4 and have 3 Border Collies. One is a 15 years old so doesn't go in the car much, but the other two like to travel. On the covers that you have, how wide are they. I measured the Prius and it is barely 50 in. wide and all these seat covers say they are 54 in. wide. Do you tuck in the extra? The dogs also use a seatbelt harness so I need access to the seatbelt. Do you just tuck in the extra?