Attaching the straps

Have you ever added an enclosed strap, only to find that the enclosure is too big and hanging off, or worse, too small and your strap is sewn along the side and all wonky? If not, then you can stop reading - you are a better person than I. I have this problem a lot, but I think I figured out a solution as I was making this apron. I'm going to share with you what I did.

Starting off, here is the apron body with the straps basted into place. The piece you see the wrong side of is the side facing which will enclose the straps. It is all pressed and ready to go.
First, line up the facing with the band, matching notches, blah, blah.
Now, feel for your strap inside the two pieces and mark the edge on the wrong side of your facing piece (where you will be stitching). Then make a perpendicular mark from the apron edge to your line.
Same thing on the other side. You can see that this one is a little tricky due to the curve. Follow the edge of the strap only for a few millimeters here and then come back up to your seam allowance. You can see where I drew in a little curve to remind myself. These are your new sewing lines. Ignore your seam allowances for this bit - they will only get you in trouble. You can grade back up (or down) to your seam allowances once you have cleared the strap.
After you have stitched, but before you trim your seam allowances and finish your seams, turn out your strap and be sure that the corner is tight. If it isn't, stitch again. You can see that I had to add an additional line of stitching an eighth of inch or so in.
Trim and turn - Viola! Perfect squares with straps coming out exactly where they should and no fabric hanging over the edge.
And at the waist. Also perfect!

I hope this is helpful. If you have any tips, I'd love to hear!