Do you have the option on your sewing machine to lessen the presser foot pressure?

If the stitches were okay when you first started but got smaller as you went along it is most likely due to drag. Keep the fabric up on the table or over your shoulder so it allows the machine to feed it through without the drag. I also agree with sewing in one direction only to prevent puckering. Trying on a sample will let you know if the machine is stitching correctly but it will not help to determine if drag is the problem. Keep trying until you find the solution but maybe on a larger piece of fabric you don't mind losing?

Turn of CC to see the text to write down the recipe.


Oops should be turn ON CC

remember to relax and take it easy you do not have to have it down to the fastest speed.

Here's another vote for using Elmer's Washable School Glue or something similar that will wash out -- perhaps something you mix up yourself, as others have suggested. There likely are recipes for that online, or perhaps even in the search function on this forum. Find some YouTube videos on glue basting, and study those. Since I've been doing glue basting I have no puckers in my quilting. I think you would be very happy with this method. Of course you must get the washable kind of glue, and yes, it really does all wash out.

Wonder how things are going with your project? Recently I made a smallish quilt with poly batt (also for a charity) and found if I placed my open hands flat on the sandwich as I stitched, that it kind of deflated the “poof” so that no wrinkles happened. Over the years I have tried many basting methods, but always come back to my pinning, it is kind of contemplative as I work my way through the quilt. Sure hope you were able to find something that worked for you! You could set your ironing board up next to your machine to help take the drag off the sandwich.

I use 505 spray baste, but I absolutely love your idea!

I've gotten puckers on the back when the fabric is too soft and pliable. Starching the backing works to hold it in place for me, and I use pins to baste with cotton batting.

my opinion is not that the basting is the problem, but with your sewing process. My first thought was to use a walking foot, but you already are. My other thoughts have already been mentioned as well. lessen your pressure of the foot on the fabric. make sure the quilt is supported on a table as you go. stitch slowly. reposition your hands and the quilt bulk frequently.
My other thought, if you are a new quilter, could this be an old machine? I had this problem in the beginning (though it didn't bother me like it is you!). When I bought a new machine, it was sooo much better. My first machine was given to me as a hand me down, and even though I had it serviced, it just didn't do well. I didn't know it wasn't good since I didn't know anything about sewing. My new machine was nothing fancy or expensive, but i found it so much smoother and cleaner to sew with.

I had that problem with a quilt I sandwiched using spray glue. Figured out that I had stretched and clamped the backing too tight. Released all that and it was ok.