if possible, roll up the quilt from both sides into the center and leave it that way for now. starting in the center, quilt to the inside edge, unrolling as you go. the part under the arm will unroll, giving you less and less bulk. keep going until you finish at that edge.
remove and turn over. reroll. starting from the center, sew to the now-inside edge. keep unrolling as you go.
if you keep a small table to the left of your machine to take the rolled-up part, that will relieve a lot of the weight. other than that, the quilt weigh what it weighs.