I feel your pain! I just finished a t-shirt quilt, it was 80 x 108, I had the same worries. First I SID around all the shirts and sashing, then went around an element in most of the shirts, like the Seattle space needle and then along the mountain lines, the numbers on some of the shirts and then just straight lines in others, there were a few airplanes that had Indians sitting on them, I just outlined the planes and unless you look closely the lines are hard to see. The back of the quilt was cool with the different motifs. The "thing" weighed 8 lbs. when done. In the past I did one that had "I Love Lucy" backing so I made a large heart, laid it on the quilt front wherever I felt needed extra stitching, marked it with a blue wash away pen and followed the outline. I was very pleased with both quilts.