I think your pineapple pillow is absolutely gorgeous. Corners can be a bit of a problem and several others have shared their solutions. I make lots of pillows for a boutique project I participate in. When I stitch the corners I sew the corners with two to five bias stitches depending of the thickness of the fabric being used. This allows them to turn right side out smoothly. Pillow forms that you purchase typically have corners that aren't full. I make a small slit in the back of the form and stuff the corners with fiberfill and then slip stitch the slit I make. This makes a smoother corner than just stuffing fiber in the corners after you insert the pillow. I also like to use contracting cording on many of the pillows I make and this method keeps the cording even in appearance.