you leave them like that, they are suseptable to snags, rips, and or tears. You really need to tighten them up by redoing or adding more hog rings and pulling them more taught. I did mine with the help of a friend who was an upholsterer and without his help I would never have go the results I did. If you notice there is no wrinkle or play in my material and alot of it has do do with the fact that we pulled the hell out of them to get them to conform to the cusion. I did mine in 1997 so you can see they held up well. Do it over or just try to fix what you need to. You'll be happy you did.
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Mine are Katzkins but no matter what cover you use the same principles apply...