Tracy_Lit5

I am making double oven mitts and when I quilt it, there's to much puckering.
In the image I'm attaching the red is the top layer of the mitt.
The lines are the quilting lines.
There are 2 layers of padding inside between the top and the bottom back layer.
My problem is that when I quilt it together (on the angle), the top layer always shifts & puckers.
1 ) I spray baste all the layers together
2 ) I start at the center and work my way out...always going in the same direction (top to bottom to the left, then top to bottom to the right)
3 ) I've tried starting at the end and going across....it still puckers
4 ) I've tried putting pins throughout the project...it still puckers
5 ) I've tried basting the top layer to the batting loosely...it still puckers
6 ) I've tried basting the top layer taught...it still puckers.

What am I doing wrong that causes this problem...and what can I do to stop it?
(The second image is a finished product using the chili peppers fabric.)

Thanks,
Tracy