I have 2 wings back chairs that are 25 years old -- when I bought them they were called Queen Anne chairs!  They needed help.  I took a chance on these slip covers.  They are not perfect but I am happy with them.  I don't think you will get perfect unless you reupholster -- especially on an older piece of furniture as the size changes.  I like that there is a separate cushion over.  I did use upholstery pins -- I really think you need to.  I did have excess on the sides so I folded it over and pinned it.  Is it perfect?  no.  Does it work?  Yes -- at least for me.  My chairs were burgundy -- it was a big color in back in the day -- and it does not show though the light blue at all.  The lighter color makes such a difference!  Overall, I am happy.  $100 for 2 chairs vs. buying 2 chairs in a room that seldom gets used or paying as much to reupholster as buying new chairs.