When I need to widen my quilt back I prefer to place the inserted piece or seam on a diagonal. If it were dead vertical it would become bulky as it was rolled up on the longarm roller and would distort the quilt back. Also, trying to get the seam in the center is an exercise in frustration. If it becomes just a little off while quilting, it will always look...a little off. So I deliberately make it off-center.
Some may say that the seam will get more wear when the quilt is folded in the middle. I try to fold my quilts in a different way every time, isn't that what has been recommended by experts? And folding a quilt in the same way turns the fold lines into permanent creases and can cause fabric damage over time.
Here's a pic of back art on a quilt I entered in the 7 Sisters show last month. Sorry the pic is so big.

yes in the cener. :thumbup:

I like it in the center, It just looks nice, and that's the
way I was taught also.

Your quilt back is really nice and I find the design very pleasing!

:thumbup: :thumbup: :thumbup:

I do center the seams. In case it is turned over, it just looks nicer, more finished, than not.

This is why I piece my backs with leftovers from the from!

I've never had to piece a back. I haven't made that many that would require it. On the ones that did, I used 108". If I had to I think I'd go with the diagonal seam. Makes the most sence to me.

As an afterthought, If I had to piece a back I would go with leftover blocks for more interest. Not centered, of course. I suppose there are many different way one could do it depending on that individuals thoughts. To each their own I guess.

I didn't even think about it. I sewed what I have together for the backing. There will be that seam in the back. Oh hell, now I have something else to worry about? I'm making this quilt for someone.

I usually buy flat sheet from walmart and use it for my backing.

You took the words right out of my mouth!
Alot of quilters dont know what a problem a
seam that runs the lenght of a piece causes
a LA.