Thread basting tends to be rather loose. Yes, you get far fewer holes, but you also get much more movement of the layers, leading to wear spots, sheering, and gaps. Take a look back at the recommended quilting distance of the insulation. This might help with 'tying' the quilt,. Rather than continuous LINES of stitches, you can 'tie' the quilt at intervals all over. Here's an explanation:

You do the ties at the recommended distance apart for quilting.

Quilters often use bunches of decorative threads for this method. You can also use bar tacks on the sewing machine or other decorative motifs, though machined methods tend to squash the pile down more than hand tying.
Mad sewing witch!