It will work with almost any size center as long as you figure the inside border width correctly. That's why I love EQ so much; I can bump up the border width until it does match perfectly.

In the version of the quilt on Elizabeth's site, are there two different colors of background used in the alternating quarter square triangles? I wondered if that was the reason to do QSTs instead of just setting squares.Or maybe I'm just seeing an illusion created by the quilting?

Gorgeous quilt - OMG!

Well, I'm neither QuiltnNan nor MTS, but here are the steps to get a pieced border to fit without using EQ.
1. Measure the length and width of the top across the center. Subtract ½" from each measurement to get the finished length and width.
2. Determine the number of border design repeats you'll need for each border. Round up any partial units for a whole number of repeats.
3. Multiply the number of whole repeats by the length of the repeat unit to determine the actual finished length of each pieced border.
4. Determine the width of the 'coping strips' (aka, the narrow inner border) needed to bring the quilt top up to the size of the borders.
5. Add the corner square.

You still have to be careful as it can look like the blocks are fitting in the border but don't really.

I usually resort to scribbling on paper just to double check.

Case in point - this quilt today.

The version I created and was playing with was a rectangle (I was trying to duplicate the quilt in the picture)- I had the layout set at 8x9 double 9-patch blocks, each block was 9".

I originally had 19 blocks (just by hitting the arrow to increase the number of blocks) for the vertical borders and it looked fine, but it really wasn't.
It needed to be 20, and the top and bottom borders needed to be reduced by .5" to make it come out perfectly (mathematically).

Exactly, you can see the seam lines if you zoom in on the border in the picture.

For me it's usually a toss-up on which method to use...is it a scrappy background? would the fabric cuts stand out too much? how I'm feeling that day?
I don't think one is harder or more work than the other...it sort of balances out.

What do you call a throw size?

The one below is 67.5" x77" (as shown, not including the outside solid border).
You can add that on...or not and just bind it.

I alternated the coloring for the double-9-patch blocks so you can see them more easily.
The block layout is 6x7.

The inner borders are FINISHED 2.75" on the sides, and FINISHED 2.5" top and bottom.
Again, over the distance, it could certainly be eased in.

If you have an different approx measurement in mind (or shape - do prefer square?), post and I'll get as close to it as I can.

[ATTACH=CONFIG]376752[/ATTACH]

MTS, thanks for helping so much. The 67.5 by 77 is really a perfect size for me. I can't open your attachment. I get an Invalid Attachment specified message. Not sure what that is?? I would love to see your image and print it with your math calculations for when I make this quilt. I dreamt about it last night for hours so I definately have to make it.

So weird.
I saw the pic when I posted it - at least I think I did.
I'm beginning to think the trick is that you have to post ALL the pictures first before you add anything to the reply box, and then add your text around the pictures.

Let's try again.

[ATTACH=CONFIG]376799[/ATTACH]

FYI - for this coloration and size , according to EQ, you will need the following yardage:

Background - 5-1/4
Purple - 2-1/4 (incl inner border, excl outer border).
Red - 3/4

Please note the background amount is a bit inflated because of the way EQ calculates yardage of the triangles and squares on point.

Thanks MTS, that is great. I have copied and saved to a word file. I think it looks so neat with the 9 patches on point around the outside border!!!

Looks like a single Irish chain to me.