I love your wall hanging! Great job on it.
I have used size 90 twin needle for straight-line quilting, and had no trouble. One lady one time told me that if you are trying to curve or veer of a straight line, you'll break your needle. So make sure that you are stopping to move the fabric if you are shifting while sewing. Also, check that the space between the two needles accommodates your stitch width, I know on my machine, I can't use a stitch wider than 3 with the twin needles. I hope this helps.