How big are your octagons? Are you going to put batting in it? You will need to follow the suggested quilting requirements as stated on the batting package. It should say some where "recommended quilting no farther than ____ apart" I would think the closer the better for quilt that will probable be washed often. Depending on the size of the blocks maybe just stitch between them to anchor. Also you could try spray adhesive to sandwich since it may keep minkee from stretching so much. Good luck!!!