Using shadow stitching to get to the blind spot would never work in a million years. Because not only is Hinata able to simply move her head to cover up for that, she can also still see Shikamaru and the Shadow to a certain degree even if some of it is within her blind spot, as not all the shadow and certainly not Shikamaru will be within the blind spot, and for such a thing as you mentioned to work, it would mean Hinata would be stupid enough to let Shikamaru end up behind her. If she's able to keep track of him constantly [which Neji failed to do w/ Kidomaru], which she would be able to do due to her 20KM radius vision, he'd never be able to take advantage of the blind spot. Plus, for the sake of argument, if Shikamaru and his shadows both somehow manage to fit into the blind spot [which would be impossible], Hinata, w/ her radius of 20KM, would be able to notice she's lost track of them, and promptly turn her head. I mean, really, it isn't that hard to do.
How would he win then ? No prep or back up.