Hi-- I want to make a disappearing nine patch for my backing --- my top is 85.5 x 90"-- how large would you suggest making my 9 unit squares ? Don't want to spend a whole lot of time on this- but wanted to make the quilt reversable. Thanks

Having both the top and the backing pieced can make quilting difficult.

Oh-- I didn't know that-- then perhaps I'll just go ahead and make a standard back-- thanks

It's also a bit of a challenge to get both layers to line up "exactly"

You gave us the top measurement only. What pattern did you use?
I did what you are suggesting once and didn't actually quilt it, I tied it instead. Turned out quite nice, as I used a high loft polyfil, so it is one of those cuddle up, fluffy type quilts. Besides that, it took such a short time to tie it (queen sized) as you can tie it at random 8 to 10 inches apart.

from a longarmers point of view, a pieced backing does make it hard to quilt. Keeping things straight from side to side isnt too bad, but its almost impossible to align top and bottom so that it comes out even.

This is good to know. I need to back off with my "creative" backings.

Ive had quilts come in with backings made from fat quarter size scrap pieces and that works fine........ mainly because its not a 'set pattern'.
Enjoy your quilting!

Don't back off! It's a great idea, and can be done. Just make it a little oversized for the extra around the back instead of trying to add borders to make it oversized for that. then there is not so much lining up to do. you will lose a bit of the design around the outside, but with a d9p that is not going to be such a big deal and you will have a beautiful reversible quilt!

All my backs are pieced. "Creatively." ;-) Never had a problem.

And as long as you're not trying to "exactly" duplicate the setting on the front, then you don't have to worry about "matching" up.

But if you leave enough room for your design/layout on the back to float a bit, any longarmer should be able to make it work. And if they can't, find a new longarmer.